It's supposed to have the thinset smoothed out a bit so that you can't see the marks. A lot of tile guys don't realize until it's too late that glass is see-through. It's normal--it's not correct--but it's pretty darn common.

Or they backpaint the glass tile.

They should have back buttered the glass tile so that you can't see marks.

Corduroy pillows are making headlines!

Any glass that isn't glazed on the backs needs to be back buttered, some need the cuts addressed in the same manner. Appliance touch up works for that, depending on what the glass color is.