I think the pattern is busy enough that most of us never see any problem at all, whether it is a two color or multicolor.
The non-quilter especially is looking at the overall and not the particulars.
I think what happens with these is that yes, we square stuff up but each time it's just off a hair, a thread, and it all skews a bit. That would be the advantage with the paper piecing with maybe a stiffer paper than ideal.
So, if you've done the final trim and all the blocks finish to the same size, I'd just stack them up and put them together instead of sashing -- unless you can think of a cool way to reconnect those sashed blocks via the quilting (because my mind just doesn't go there).
I say (because it's true) that I find it somehow comforting that I never have to deliberately put in a mistake to my quilts to keep myself humble. Even the simplest, easiest thing ever -- there is something in there I'm not happy with.
What's our saying around here -- Finished is better than perfect? And then my other saying is I always have next time to achieve perfection. Still working on that...