I don't have any real experience with it. A shower floor is required to have a slope to the drain and you can't slope 2' x 2' tiles - they will crack and break. The only exception to this would be if you have a channel drain running along one of the walls so all of the slope goes in one direction (vs a drain out in the center area of the floor somewhere). I wonder about who advised you with the design of your shower and they didn't know this. The max size we will use on a shower floor is a 3" x 3". I have seen some contractors use 4" tiles.

If you do have a channel drain and you can achieve the required slope even with a large format tile, I would agree with your contractor that it could be a slip hazard.

I do have the Inifinity drain designed for large scale tiles. Thanks for your comments, Deborah.

too big for shower floor -- the grout helps you have traction. I would use the one by ones that match your large format tile or you could use the 3 x 12s.