The physics were the same, but you assume our current understanding of physics is complete.
At least until we solve general relativity vs quantum mechanics (theory of everything), I would be hesitant to claim we know enough to state definitely what is or isn't possible.
One thing that both GR and QM agree on is that the speed of light (well, the speed of massless particles) is a constant of nature.
We also know this very clearly from relatively simple direct measurements: there never was and there never will be a way for matter to accelerate to speeds greater than c.
Or plot twist, the year is 4765. Turns out physics is deterministic, the universe still may or may not be a simulation, but that hardly matters because the only variable in it is human experience. While interstellar travel remains impossible, we can perfectly simulate any point in spacetime to enter as our reality. We create our own multiverse out of curiosity, powered by other verses we simply run backwards to restore entropy. We no longer know what's a simulation, nor do we care and choose difference experiences for lifetimes for infinity.
plot twist, the year is 7654. Turns out earth is flat.
The likelihood of your statement is similar to that of mine. It's just nicer to conjecture about the former because the increased complexity brings the illusion of potential.
They allow for the galaxy to essentially possibly be shorter than seems visible - they don't really allow for these to be created if they don't already happen to exist.
It is not complete, but you're assuming that our current understanding of physics have major deficiencies where significant prior observations can be overturned.
Even Newtonian physics 300 years ago largely remain the same, relativity complemented it and explained issues on edge cases. It did not completely overturn Newtonian Physics and gravity did not became repulsive instead of attractive.
At least until we solve general relativity vs quantum mechanics (theory of everything), I would be hesitant to claim we know enough to state definitely what is or isn't possible.