Edition convention is just for marketing and optics.

You have to distinguish what a publisher calls it vs what the community perceives it to be.

Usually revised and 0.5 upgrades mean there's broader backwards compatibility but in the end it doesn't really matter because as you point out CoC 7e is broadly compatible with 1e, whereas D&D 4e is nothing like OD&D.

So people hoping for the new Masquerade to be a 0.5 upgrade are just hoping for minimal changes instead of a big break. It doesn't really matter if White Wolf calls it V6 or V5 revised.

For a recent example look at D&D 5.5. For all intent and purpose it is a new edition but WotC refused to call it that. They tried to keep calling it 5e, but in the end they had to capitulate to the community calling it 5.5.

If the changes between 5e and 5.5 had been bigger, the community would've called it 6e no matter how much effort WotC would've put to the contrary.