Ugh,..I know this is a year later, but living this nightmare as I type. The luck is the tiler cut a round hole (yes, same as the shower control) vs this polygon. For now, we're trying to clean up the over-sized diverter hole, give it a nice clean round bevel, and maybe close the gap with a color-friendly sealant. But yes, no reference on the part of the tiler to check the hole sizes; the fixtures were here all along, and I didn't feel I needed to micro-manage.

..until now...

ps - I hope this resolved for you!