@scottjenson not at all!
I think the Readme for the API task force covers it pretty well.
https://github.com/swicg/activitypub-api?tab=readme-ov-file#introduction
tl;dr is that social applications on ActivityPub are often built as an integrated client-server stack.
In other ecosystems, like the Facebook Platform, app developers could leave the complicated parts of storage, authentication, social graph, and distribution to the platform, and they'd just concentrate on innovate experiences at the top of the stack.