"Quality" is a very subjective idea. Yes, docs are easy to keep consistent over long stretches of time if the speed of evolution is slow and a small number of like-minded assiduous gatekeepers can vet every change from a small number of contributors, but since the speed of evolution is slow, OpenBSD for example still has a giant lock protecting most of the kernel -- this despite nearly 2 decades of multicore chips shipping pretty much everywhere.
Any growing project will always suffer from consistency problems -- humans just aren't capable of scaling to the point where a single hierarchy can consistently manage a monstrously large system. Linux doesn't have a 'base system' quite like OpenBSD: coreutils, libc, bash, and 20 other similar packages all come from a large variety of differently minded maintainers across the world.
Viewed from a macro scale, OpenBSD's consistency breaks down immediately upon starting to install stuff from the ports collection - sure the base system makes a great firewall and basic HTTP server, but to use anything popular you pretty much immediately end up with ports. And the quality standards there are identical to Linux land, because it's the same code.