1. Free software is an ideological battleground, and as long as you abide by the license you're fine. Most GNU packages.
2. Open Source without a single backing entity is a meritocracy (or tries, sometimes a little too hard) and you can help improve it for everyone. Like the Kernel.
3. Open Source from a single backing entity is an insurance policy against that company failing or overcharging - at least in principle - if that works is often up to adoption, see the state of various Hashicorp products and their forks. You'll also never get your PR merged if it isn't critical, you aren't a customer or the PR misaligns with the company's strategy. I've even seen this happen on an Apache project, so that's not a guarantee of being group 1 or 2.
Matt has always pretended he belongs to group 1 with incidentally aligned commercial interest, but it turns out WordPress is group 3 with a server dependency twist. He wouldn't even approve a config constant to change the default update/catalog endpoints.
He probably is trying to make a point what WPEngine is doing (based on his own perspective)