Hi Carole, the internal corners should not be filled with grout. The gap is filled with flexible silicone, so that it does not crack due to heat expansion. If it is filled with grout it will crack, it is not the way it should be done.
I'm not saying all contractors working on commercial projects such as hotels and new builds are bad, I have seen both excellent and some shocking examples myself.
If you are having problems with mould growth, then you need to ensure your background is prepared properly, use suitable grout protector, and a decent mould resistant silicone (preferably matching your grout colour, so it look like a grout line). Plus using a proper cleaning product, to remove soapy residues from grout and tile surface once every few months, should all add up to keeping it looking like new.
Also, if your tiler uses a silicone shaping tool, and cornertape/masking tape, then the silicone joint will be nice and tidy. Not sploged in and smoothed over with a finger, which I guess is what alot of people are used to seeing. So, just because your used to seeing something done a particular way, doesn't mean it is the right way to do it!!
Good Luck