There seem to be two separate issues here. The spackling: I DO think that one should spackle prior to painting. I'm not a pro, though, but I've always spackled first. And always taken off the plates first.

The second issue is the paint sheen and color. It seems like you OKed it prior to painting, since he was telling you about the floor and all. If you wanted flat, and a different color, perhaps speaking up then might have been good, not that it helps now, I know.

Not knowing what transpired before paint hit the wall, I would say there has been a communication breakdown between you and your contractor.

Actually I shouldn't have mentioned the paint finish and color since it was a separate issue and not his fault, just my bad judgement.

But I would really like to know if it's standard for painters to leave on the wall plates and not spackle prior to starting to paint. How would it be possible to fix the cracks, etc after the first coat?

No, it is not standard at all to patch in between coats. If it is an eggshell finish, the patchwork will flash for sure if not double coated. Sometimes it may be an allright idea to patch in between coats if the paint is flat because you can see what needs to be repaired better. This is mostly true though when the walls are really beat up. Wall plates should also be removed prior to painting. Leaving them on is apartment painter hackwork.