I have a 32-inch wide non-load-bearing partition wall that only serves to hide the refrigerator in an open floor plan. The house was built in 2020 and is in a cookie-cutter type subdivision. The general construction quality is maybe a "B". From the outside wall of the house the floor drops about 1/4" under this wall This wouldn't be noticeable, except that the baseboard is level. Poking around in the gap there does seem to be a bottom plate. There's no cracking or damage to the drywall. There is a storey below, and there is no obvious bowing or out-of-level to its ceiling in that area. The floor joists run perpendicular under that wall segment. The flooring is wood laminate.

I guess among other things what I'm trying to understand is, is this more likely something that happened after the house was completed (settling) and there was no gap there when the baseboard was fitted, or something that was there before the trim work, but the laborer doing the trim didn't have the skill to adjust for? IE, not knowing how to do the set of compound mitre cuts to get the pieces of trim to lay flat against the floor around the wall.

PS

I know that's door trim not proper baseboard trim, but that's what they did. New home construction now ¯\_(ツ)_/¯.