I mean yes, this is obviously a thing, no argument. But I'm not sure that means that Open Source maintainers are feeding themselves off the goodwill and feelgoodness they are getting from maintaining these projects.
I would gander to guess that most maintainers are supported by a small minority of enterprisy agreements they have, either through large sponsorship or by working for a company that is supporting their Open Source work.
And I think that's a bad thing. I would much rather see them supported by 10,000 $1 monthly donations than 5, $2,000 donations. That is more likely to lead to features and attention focused on the needs of the masses than the enterprise.
I say this as someone who maintains an Open Source platform primarily funded by a single enterprise. I would love to flip that on its head.