Do I need to use epoxy thinset and grout when installing mosaic tile less than 2” square?

No, ProTile™ HD and ProTile™ HD1 shower trays are designed to accommodate the heavy point loads, typically found in tiled shower systems without requiring the use of expensive epoxy thinsets and grouts. Heavy point loads occur when wheelchairs or other physical assist equipment are rolled across small mosaic tiles and pebbles which can cause the tile or grout to crack. ProTile shower trays are designed to support these heavy point loads.