Rational ignorance. The bash warnings about non-POSIX features have a reputation for being unreliable, so if I've only tested with bash (because I don't care enough to set up chroot) I shouldn't claim it works with any other shell.
Well ... maybe using a shell to run a command worked differently in 1971. There's $IFS ... job control ...
Okay, yeah, there has never been a shell on which that wouldn't work. WTF bonus points for requring /usr/local/bin, which is almost certainly not where the OS maintainers package it.