Sandy grout is usually used on the floor tile, I never used it on the wall, because depending on the tile it can be easily scratched.

Also, the outlets on the backsplash are usually installed at the same height unless it was requested otherwise.

Grout width determines if sanded or unsanded grout should be used. Standard grout widths larger than 1/16 will shrink if unsanded grout is used. Those are 1/8", and the sanded grout is perfectly appropriate for that type of tile and that joint size. A better quality grout, with a micro aggregate, like Mapei Ultracolor Plus FA (Fine Aggregate) should have been discussed on the front end. The $5 more per bag is totally worth paying for, but it isn't coming out of your installer's pocket. Nor is the extra time required to deal with the extra bit of cleanup effort. Having buyers remorse on the hind end is useless. You get what you got, because you didn't discuss options on the front end.