Tile – Our tiler put Grout Boost on after laying grout, thinking it was grout sealer. What should we do

I wouldn't be too concerned unless there's mortar that is raised above the level of the grout - which you've already said there isn't.

Scraping the higher sections to give a reasonable depth of grout would be as far as I'd go.

A lot of adhesives these days are sold as tile cement and grout, though they do tend to be coarser than "pure" grout, so they are basically the same material. However, a pure grout does give a smoother, "cleaner" line.

Floor tile grout also tends to be coarser - I suspect to be able to cope with the higher degree of wear and tear it will receive compared to wall tile grout.

Very nice looking job Jared, congratulations! It is very normal for unsealed grout to change to a darker color when wet. This will happen even with fully cured grout. Feel free to buff any excess grout or haze off your tiles, it won't hurt anything and that also is normal for newly installed tile. If the darker color when wet bothers you, then go ahead and put a couple of coats of grout sealer on after about two weeks from the original grout date. Even though the manufacture claims stain resistance, it does not claim to stop the temporary color shift when wet. Sealing the surface of the grout will stop the wetting of the grout and end the color changes. You may find you need to reapply some sealer every year or so in a shower surround. Apply the sealer with a small foam brush just to the grout, Buff excess off the tiles 15 to 20 mins later. Looks Great!!! Good Luck.