This is the best question, because my gut is that "feature" that it touts over AP is much more a dangerous bug.

This is "take it with you."

What "take it with you" does in the ATProto way shores up and makes more robust the permanence of what you post. Sounds good, but also potentially harmful in terms of surveillance et al.

The ActivityPub approach is less robust and theres more room for deletion and non-reliability. Which in some ways is bad, but also helps in terms of "plausible deniability."

In other words, if you're Big Brother, you much prefer ATProto.