What’s your concern exactly? At first glance, everything looks good.

How would he fix it? Are the walls all exactly plumb and square (none really ever are)? If not there is your reason. It happens, he is a tile installer not a miracle worker as he is not going to reframe the house.

The tiles are against perfectly level molding

Thank you! This is what I was going to recommend but didn’t know whether it’s feasible.

The window trim appears to have a problem and/or the tile is so thick it meets the trim at a radiused edge. May work better replacing the window trim with a deeper profile.

It’s an optical illusion. The black grout was put on to wide and thick. The window trim is fine.