your contactor is the problem. the shower floor should be water tight regardless of wether or not there is a tub in there- this brings up a huge red flag- beware

Agreed.

yeah, I was just trying to describe to him without this picture and he was having issues with the idea of the tub drain pipe going through the floor of a shower. I think he's just never seen anything like this before

Agree with the comments above. Also, note that the floor in the photo is sloping away from the tub (drain is in the foreground), and I would assume the tub is caulked at the floor. With a good contractor and tile subcontractor, I wouldn't expect for this to cause a problem

This project had a concrete slab floor, the entire 'wet room' was waterproofed as if the entire thing was a shower, with waterproofing running to the top of the tile.

We are doing the same thing for a client... and we are having issues with how to drain the tub. The shower pan has the hole for the drain for the shower part... but there isn't an additional hole for the drain for the tub. Our guys are saying if we penetrate the shower pan to make a new hole, that it is likely to cause problems down the road. Please explain how you drained the tub. Any help is greatly appreciated!!! Thank you!