A replacement baritone neck for a Strat or Tele will assume that the bridge is in the standard Strat/Tele location and the frets are all positioned accordingly (you normally end up with 24 frets rather than 21 or 22 as a result). No movement of the bridge is required. So all that happens is that the pickups are all proportionally further towards the bridge than on a standard scale length guitar, so will have relatively less bass content.
A purpose designed baritone might have a 22 fret neck so the pickups are spaced out more. Then the neck pickup will be nearer that 22nd fret and have a lot more bass in the sound.