Velocity determines trajectory, which determine accuracy at distance (group size)
If gravity wasn't a "thing," and bullets didn't drop over distance, then 28 fpswould be the same as 2800 fps.
But.... it is and they do.
Now... once you determine velocity and can predict trajectory over distance, then no, it doesn't really matter. If all you do is shoot exactly 600 yards, then ...right....who cares? But... Velocity is *very* important in PRS matches, which fires over numerous known and unknown distances in a single match. It drives match scores.
Alot of the velocity conversation is just "bigger johnson" stuff.... bragging rights over how fast my bullets go, and how often I get to replace barrels, making me one of the cool kids. Some of it is the preference of a flatter shooter over longer distance.
Or am I missing something in the question here?