it feeds those values into jumpspace with a relative velocity of 0,
Relative to what? This is the problem. You're solving the problem by pretending that there is a single resting frame of reference in the universe (there isn't). In which case you can drop the "relative" term.
You can say that all the stars and maybe the planets too are sort of sitting in space, or perhaps pinned by giant celestial thumbtacks to a cosmic corkboard. They'd have to be pinned, I guess, unless you also decide there is no gravity - things would start moving immediately and we'd see a Universe Sandbox style smashup. There would be no seasons, no waxing and waning of moons, no orbiting anything.
Of course, your Traveller universe is imaginary, and your cosmology could be turtles all the way down if you want (Wikipedia has a nice article, if you're not familiar with the phrase). The problem in a Traveller context is that as science fiction, the players often want to interact with the science bits and if cosmology, the physical characteristics of space, the astrography of space, the fundamentals of physics, are re-imagined from the ground up, the referee has to do a massive amount of work, and teach it to the players, so that they can feel immersed, and so that they can think their way through the challenges you put in front of them (which is, IMHO, a major part of scifi adventuring). There is a danger that the referee just makes stuff up as he goes along, and every interaction with the environment becomes referee fiat - this can be ok for a time but does tend to rob the players of agency.
This is why many referees assume the physics are the same in the Traveller universe, except for some concessions to scifi tropes so that we can have our ray guns and rocket ships: i.e. J drives and grav tech, but still have a place that makes sense and works in knowable ways.
These concessions raise questions about their interactions with real physics, prompting efforts to reconcile things so that there is a consistent universe in which the players understand the rules. That is why we are all trying to figure out whether you keep your vector when you jump; it is a thing to which there is no correct answer, but there are answers that limit some the game problems, while raising others - whichever assumption you make you have to find a way to deal with the resulting game problems but this is better than not being aware of this, and suddenly having things fall apart when the players decide to push the envelope, or ask annoying questions. The zero velocity idea opens a whole can of worms best left closed., however, because it blows up everything in the way the real universe is structured. If your players don't mind you not letting them peek behind the curtain in case they see the turtles, you'll be fine, but IMO you'll be missing out on the whole point of scifi.
A poetic description of the crux of the problem, with credit to Monty Python, there is a video on Youtube with singing and dancing:
The Galaxy Song
Whenever life gets you down, Mrs. Brown,
And things seem hard or tough,
And people are stupid, obnoxious or daft,
And you feel that you've had quite eno-o-o-o-o-ough,
Just remember that you're standing on a planet that's evolving
And revolving at 900 miles an hour.
It's orbiting at 19 miles a second, so it's reckoned,
The sun that is the source of all our power.
Now the sun, and you and me, and all the stars that we can see,
Are moving at a million miles a day,
In the outer spiral arm, at 40, 000 miles an hour,
Of a galaxy we call the Milky Way.
Our galaxy itself contains a hundred billion stars;
It's a hundred thousand light-years side to side;
It bulges in the middle sixteen thousand light-years thick,
But out by us it's just three thousand light-years wide.
We're thirty thousand light-years from Galactic Central Point,
We go 'round every two hundred million years;
And our galaxy itself is one of millions of billions
In this amazing and expanding universe.
Our universe itself keeps on expanding and expanding,
In all of the directions it can whiz;
As fast as it can go, at the speed of light, you know,
Twelve million miles a minute and that's the fastest speed there is.
So remember, when you're feeling very small and insecure,
How amazingly unlikely is your birth;
And pray that there's intelligent life somewhere out in space,
'Cause there's bugger all down here on Earth!
