The Pro edition is basically a donate button that gets you a few themes and applications that you can just as easily install from Flathub.

Core is free. And then you install the apps to make it like Pro. Some people like everything done for them, and some businesses won't approve free software for use, as it has a stigma of being sketchy, so adding a paid version can get this past your chief technical officer at a corporation.

There's nothing wrong with giving money to FOSS projects.

In fact, a major issue with the open source world is users never donating.

I've never used Zorin and don't intend to, but the existence of optional paid software isn't why.

The answer to your question which sounds like a statment is no.