Who gives a shit, it doesn't matter. Why would he think WP Engine would pay anything they're not contractually obligated to pay?
This has all played out similarly elsewhere, e.g. to the point that some companies have started to carve out a new types of licensing so that all of the "open source revenue" doesn't just get vacuumed up by the big clouds/hosting providers (e.g. see the "Fair Source" movement being promoted by Elastic and others).
Matt could have gone down that route. I could easily imagine a million ways he could have handled this better and gotten the community on his side. Instead he's acting like a collosal asshole.