Maybe this is, but I do not know the answer to it.

In order to remove a bathtub to replace it, you have to undo the drain. Now
can you do that somehow from inside the tub, or do you have to go through
from the ceiling below it. How the heck do you get at the fittings without
doing that? The tub goes righ to the floor at t he front and there is not
enough room at the back to do anything....

???