Basically, yes. EEE is a strategy developed by a dominant company whose revenue stream came from paid proprietary software and services but which embraced open standards with the goal of vanquishing the threat to their business model posed by that openness and maintaining/recovering their proprietary domination.

Does ActivityPub being open and used by many different projects & organizations pose a threat to Piefed's business model? Is Piefed a powerful company that built that power on a proprietary model and seeks to preserve that power by embracing, extending, and extinguishing ActivityPub? With the goal of maintaining/recovering proprietary domination?

No. So it ain't EEE.