someone just plain lying about what OS they're using in order to break fingerprinting.
The idea with avoiding fingerprinting is to look like whatever the biggest group of users looks like, because that's who you share the fingerprint with. If you use an uncommon value for something, you make fingerprinting easier.
That's one of the reasons why for example Vivaldi on Linux sets its user agent to match the latest version Chrome on Windows.
The comment you replied to is a direct reply to the comment you linked - I don't think it was intentional, but if it was, then I'd like to say it's not a very helpful reply as OP already read it.