Yeah that sounds well plausible, especially because there seem to be many (minor and major) versions of bash still around in different contexts. Not to speak of any other shell. Escaping seems best!

The "bad interpreter" being there or not might be OS-specific, though. Unless some bash versions use fork+execve vs. posix_spawn or similar and that makes a difference there. I haven't checked. Overall I can see how even some current stuff might give the confusing message...