From what I can see on the photo, the two floors were poured at different times and poured the way we see it.
It could be possible that one floor was poured while the door was not there and a guess was made on the floor elevation.
One of the two floors is also out of level.
It appears that the high floor was chipped away from another portion of a wall or floor at one point.
This area of the slab could lead to future water intrusion if there should be a drainage problem with the property and hydrostatic pressures of any kind.
David,
I would call out a trip hazard. I’d recommend repairs to smooth the transition from one floor level to the other, using approved material such as floor leveling compound installed by a qualified contractor.
I wouldn’t report or comment on what may be present in areas that are not visible, as that would be guesswork. The presence of a cold joint isn’t necessarily a bad thing, it’ s just a thing. Do your best on the moisture/mold/drainage issues and move on.
Stu