Shluter profiles come in several sizes. Make sure you have the correct trim for the tile you are using ie. 1/4" trim for 1/4" tiles. The trim goes against the wall, the holes allow the thinset to lock in in position.

The profile is not even resting on tile properly in the #3 pic regardless who bought it A few hiring tips for anyone reading , Always ask the prospective tiler whos going to install, is it you yourself or do you send in the B team , the C team etc. Secondly you will know when you have a tile pro in your home, they will start getting less and less interested when you start declining having them order purchase and supply every last bit of tile related material for the project its not always about profiting or markup but more about risk and having a smooth project , this also puts the liability in your favor when things backfire vs attempting to shave a cost. One must ask themselves if they know enough about the tile business to be qualified to guage the prospective hires "knowledge"as well as select and purchase the correct materials . There is so many new products, methods , industry standards and a million hacks out there coming in with low rates willing to engage in sharing liability be very careful in the hiring process. @OP youve got the C team and i think the B team is on vacation here

It starts with the appropriate design. Without seeing where these dropped areas occur my first thought was if they could have been dry walled and been painted to be a part of the ‘ceiling’ and not tiled at all as part of the ‘wall’. Not to necessarily drop the whole ceiling. So assuming it HAD to be tiled you and your tile pro discuss the overall design and details. A seasoned pro will know the tile sizes in relation to the spaces are either working or not. If you hired a handyman type who is just ‘doing what they are being told ‘ then you own this. I have to question if they have waterproofed properly because any tile pro who knows their stuff would have questioned those tiles used on those slivered areas (regardless of wether or not you got the correct schluter edge ordered).

@segbrown - It certainly could be done during tile installation. This type of shelf is not a after thought. If the tile is not installed simply reduce the size of the niche.