So, yes, if you make those assumptions, which is certainly reasonable. Those assumptions are not actually made by the game rules, though. Grav tech is not dirt cheap stuff any rando has at the TLs that most trade ships are operating at. Sure, at TL 15 ports or whatever, but these ships are built at TL 10 to 12. And, yeah, sometimes they say you can control the grav plates to be free TK, but other times they don't.
The current Mongoose version of the Type A has some gantries, which is why it's cargo hold is smaller. The 1e version had cargo chains and stevedore bot. Older versions didn't necessarily have even that. But in the SOP they talk about having anti gravity on garden variety crates. So *shrugs* Pick what you like.
The game just says there is cargo and brokers. The cargo and brokers are described exactly the same for a TL 0 world with a patch of bare rock for a starport and for a TL15 class A starport (you can find them faster if there's internet, though

) Ships that small will reliably fill their cargo hold at that TL0 world with a class E starport. I'm sure Ea-Nasir carefully containerized all his copper ingots.
It's not that these ships can't handle any containerized cargo at all, though their hold is disastrously designed if that's what is supposed to be doing. It's that they are not expecting to rely on it and they are expected to go places that the corporate merchants ignore. Look at how many worlds have class E starports. Those are literally a patch of grass and sign. Class D starports range from that and a tank of water for fuel to the broken down remains of a once major starport with more equipment than it can use. You are talking about infrastructure for worlds that are described as seeing maybe half a dozen starships of any kind in a week, many of which are not traders and probably none of which are big tradeships.
This is what the Traveller Adventure says about the Aramis subsector:
"At the very fringe of the Imperium, in a backwater corner of the Spinward Marches, the Aramis subsector has been an undeveloped and often ignored part of Imperial society for generations." And this is about a region that actually has a pretty high average port quality. The entire Trace is B or better and half the Towers cluster, too. Though, it's possible those are all recent upgrades since Vargr trade is causing corporate interest in the region to finally materialize as part of that storyline.
And this is what it says about Imperial trade in general:
"Transport companies service trade routes to worlds that can furnish goods, ore, or products that are in demand. Other worlds must wait for the tramp freighters, the free traders, that carry goods to contracted destinations or on speculation."
I think that there is a disagreement about what free traders are. The trope of the "free trader" that was big in Sci fi when all these rules were first written consisted of stories of indie family or found family traders operating under the corporate radar, scrounging the missing bits in the corporate sector or stories of the small indie ships that pushed beyond the fringe of developed space to try to grab some wealth before the corps took that region over too combined with a few stories of small indie ships doing trade pioneering (ie going places no one has successfully traded before). And they mostly don't have good margins or the budget for fancy gear and lots of maintenance and other support.
This isn't the truck driver or the feeder ship. Free Traders are to freight liners what door dashers are to commercial truck drivers. No structure, not necessarily any licensing, dubious accountability, no one cares if they just disappear. Just used when it's not worth doing it yourself.
About 20% of the world's trade even today is "General cargo", either because it is ill suited for containerization or its origin or destination are not container ports. Another 20 to 25% is bulk cargo (mostly liquid, but some dry), and the remaining 55-60% is containerized cargo. Based on the way the published ships are designed (which, of course, can be easily modified) and the way the "ports" are described, I think that those "free traders" would be overwhelmingly in that general cargo trade.
But this is Traveller. It is designed to be able to simulate all kinds of games. So there is no reason to base your trade on those assumptions. Anti Grav can be ubiquitous. Those class E starports could have container yards and trucks and railroads leading to them. Ea-Nasir could have an imported laptop to get emails from those trade ships that do visit. More likely, the "E" or "D" starports are the public facilities and there's a much better "CorpPORT" in orbit that all the priviledged ships get to use. There's no one true way to do this and, since the trade rules are core rules not setting rules, there shouldn't be.
I don't know about other people, but when I come to these conversations it's to say "Hey, this is what I like, this is how I do things, and this is why I do that". Because maybe other people have the same interests and might benefit from things I thought of that they didn't. And I read other peoples' posts hoping to find ideas that they had that I didn't think of but like. I don't expect to agree with everyone else's ideas and I don't expect them to agree with all of mine. I don't feel like the existence of my ideas invalidates other peoples' ideas. It would be nice (for me, anyway) if more people posted "I do it this way because I want these outcomes and enjoy these assumptions" instead of "My ideas are better than yours" style posting. As I said in my first post in this thread, there's Sweet F-A for "facts" about trade 35 centuries in the future. There's facts about how the real world works today. There isn't about how it will work later. So there's no ideas that are better or worse than anyone else's. There's only what you enjoy or don't enjoy.
Lots of people have posted interesting ideas in this thread. I wish more of them were positive oriented "Here's how I think free traders work and what backwater ports are like, because I like these things and these assumptions." That would be fun to read.