It makes no business sense to "require" someone to get their hands on the stats needed to give the game a try. When people buy rules to just about any miniatures game I can think of, they expect to have everything needed to play at their fingertips.
But that doesn't mean the core rulebook must have those stats. The rulebook could have everything else, and for stats, they could say "Check out Signs & Portents for unit stats as they become available." Since S&P is free, then there is no problem. It also serves as a marketing "pull" because while you are checking through the latest issue to get to your stats, you ALSO get to see other cool Mongoose products, and that exposure can result in selling you more stuff.
That would make good business sense.
Now, let's say the unit cards are full-color-photos of the units in question, and have fancy backgrounds, and the stats nicely laid out. Those "cards" could be placed in S&P for you to print on cardstock yourself.
Mongoose could ALSO offer up those same cards, pre-printed for you, in a unit stats pack, much like their ship counter packs. You are not FORCED to buy them, because you can already get the info for free, but if you like the idea of having the printing and cutting and all that done by somebody else, then you will want this.
Charging for them that way shouldn't cause a ruckus, because the info is already out there for free.
I do think that if a customer buys the rules, and then discovers they can't even try a sample game (using cardstock counters if they wanted to, or bottlecaps, anything just to try them out) because they ALSO have to buy the "official" minis, there will be very disappointed gamers out there.
Steve