I don't actually think it would go down like that so I think the point is moot, but are we really going to go through this again? Developers should (and often do) know better than to get into these unsustainable situations, but they still do it.
I have some unsolicited advice: please don't open source something that you are actively planning to sell. Nobody will take this advice of course, because delivering your product as an open source project is an easy way to generate some leads and even get some free labor here and there. But if you don't want people to feel deceived, start with your expectations out front and magically people won't be angry at you.
On the other hand, I agree people wouldn't be angry at company B in this scenario, because they're not the ones who set the incorrect expectations to begin with. OTOH though I really do doubt "we just removed some features so we could charge you for them" would be a successful pitch as a brand new vendor for something.
I'm struggling to understand how there's even still a lot of debate on this subject because it's very simple, if you can pull off a sustainable FOSS project then the world will be grateful but in many cases it becomes very clear over time that there was effectively no plan, just a lot of hope that maybe things would work out somehow. Whatever good that is.