Super common, tapers will tell you a drywall finish is smooth not flat. Wood framing always has big anomalies as well. If you want super straight flat walls you have to frame with steel and run 12-16 ft board 5/8in or better w/ no but joints. Only time you see that is when its a commercial space. and you still end up with every corner not being a true square. The saying goes ... Putty and Paint make a Carpenter what he Aint.
It looks good, nice lighting, good flooring choice.
I often take the flooring and mill it to cap the top of the stair rails.
Do you glue it together or what?
I considered getting oak boards for the top of the rails and staining to match floor but ended up with mdf because oak is really expensive and i thought it may make the rails pop when i really don't want them to pop.
I used 16' primed mdf baseboards, I'm getting over my hatred for mdf.