small puddle a big problem or a non problem?

The contractor who just rebuilt my conventional mud shower didn't take the tilt of the bathroom floor into account (or fix it) as he should have. He's redone the curb so my door will be right, but the drainage in the shower itself might or might not be ok.

An area near the drain about the size of my hand seems to retain the shallowest of puddles. A film of water covers a few of the 2x2 tiles; it's less than a millimeter deep at the grout lines.

I might be able to improve things a bit by shaving down the fraction-of-a-millimeter exposed lip on the drain flange and ensuring that the cover plate recesses in slightly rather than sitting flush (on the low side) or slightly above (on the high side.) The depth of the water in the puddle is pretty close to the height of the standing water on the edge of the cover plate between the rim and the holes; giving it someplace to drop to would seem to be a good thing.

Obviously this wouldn't be an issue if the floor he started with was pitched correctly. The question is, how much of an issue is it now? I don't really want him to rip it all up, but I don't want lingering mold issues either...

What do you think?

I would seal the grout with 2 or 3 coats of a grout sealer and I would do this every year or 2. This should prevent mold maybe.

From your description, it appears he did NOT install the drain fitting level. That has NOTHING to do with "considering the slope of the floor". The drain should be installed PERFECTLY level and then the tile is laid to meet it, so there is no "high" or "low" side.