Ok, another thing I'm questioning with my contractor. He's going to lay the tile and said he will be using thinset in the tub/shower surround and mastic for the rest of the room. This is a 5x8 bathroom and will be tiled to the ceiling in the shower, and 4ft high for the rest. I was reading up on thinset vs mastic, and it sounds to me like the entire room should be done with thinset since it's a bathroom and is a wet environment. The walls will be 3x6 subway (with a mosaic accent strip running around the room), and the floors are 6x24 porcelain "wood" planks.
Should all the tiles be installed with thinset? And why would he even bother switching to another compound for such a tiny space?