I'm also a bit confused by the original question: if there's a proposal to > release 4.2 as 5.0, let's hear out why and just vote for it (list reasons, > and let everyone express their opinions about why this does or does not > warrant the version bump). If there are no reasons for us to do, I'm not > sure why this is important.
Consistency. To the benefit of operators. I totally get from our PoV there's no problem with this being arbitrary. But from experience witnessing the uncertainty and pain operators go through, this "decide it each time" is not simplifying it for anyone.
