As someone dealing with enterprise software for living, what he's saying absolutely makes sense, and I deal mostly in web applications (where I never really have to worry about the low level stuff).
Just because the top layer seems to be the same, doesn't mean the underlying ones are. There's a reason why perfect bug compatibility is a thing (or maybe, was, in RHEL ecosystem?).
Things that looks like slam dunks in theories are never such in practice. Weird bugs pop up from time to time; and believe me, they will!
It might be rare, you may only see it once or twice in a project; but when it happens, you're gonna want to be ready, or people will question your ability to do your job.