There's nothing special about it, they're just two English words. What makes the term special is its origin and history - specifically, how it was coined and spread by the OSI and its members.
So, they should make their own history with a new term. In time it might be more relevant than open source, and that might be great. But don't mix them up.
But as I said I would still prefer "non-commercial open source". I grants you the right to modify etc. but only if you don't exploit it commercially. Just like copyleft open source grants you those rights, but only if you also distribute the source code.
Apparently though I guess if there was something that was a red herring it is this whole discussion as someone pointed out that common clause doesn't even call the license open source.
How open something has to be, to be called open source is a matter of opinion, so is to some degree what open means in the context of open source. Otherwise they would have to call it "unconditional open source" but then a number of, if not most, licenses wouldn't qualify.
> The patent grant is a red herring; they're copyright licenses, and judged as so.
It isn't a red herring. I use it as an example to show that the openness in OSI approved licenses aren't absolute. Some licenses have other terms. They might for instance retain the moral rights of the author, try to avoid any liability or condition the distribution of software. If you can have those exceptions and still be considered open source I don't see an objective reason why you can't call software where the economic rights are retained open source as well (even though I can understand why people wouldn't want that).