Likewise if you set your implement down when it is over a hump, then that's as low as it will go - it won't drop as it passes over it. The B7500 had an additional set of side link holes on the lift arms closer to the tractor that allowed the arms to drop a few inches lower. This meant that the "ground" was not the lowest an implement could go.
BTW, the B7500 didn't have position control, so it was a different type of control for the 3-pt and that is why it had a detent position on the lever. But the mechanics of float were identical to any other 3-pt hitch with or without position control. The only limitation is the travel of the linkage.