Just revert the code back to pre-26! This is ridiculous, it can't possibly be this hard and if it is, it just points to the degradation in the quality of Apple software! This is maddening!
Pre-Tahoe windows didn't have these stupid round corners (which is the ACTUAL bug which should be fix).
This is already the pre-26 bounding box, isn't it? It's the new graphics that don't line up. (Not a great excuse, but the graphics are here to stay at least for a little while.)