As an OpenBSD developer who frequently fixes portability issues in external software, this doesn’t match my experience. Upstream developers are typically happy to merge patches to improve POSIX compliance; often the result is simpler than their existing kludges attempting to support desired platforms like MacOS, Alpine/Musl, Android, Dash-as-sh, and various BSDs. It turns out a lot of people find value in relying on an agreed‐upon behavior that’s explicitly documented, rather than “this seems to work at the moment on the two or three distros I’ve tested.”