Let me use an analogy for non-technical people to understand it.
ActivityPub is kind making glass doors and huge street signs.
Mastodon figured that some people get very upset and hurt by seeing certain things behind glass doors, so they made special doors out of the huge street signs.
So my dialogues with ActivityPub purists normally go like this:
Me: "On Mastodon, we use street signs as non-transparent doors"
ActivityPub purist: "That's a wrong way to use street signs, you have to write something on it and point to a glass door"
Me: "No, people here took what you produced and fashioned it in a way to increase the safety of this space"
ActivityPub purist: "You don't understand anythin, signs are for writing, doors are for opening, we figured it out in our club so you have to deal with it".
I hope that the analogy is clear. I had a lot of conversations like this, so now I'm aggressively muting people who are misusing CWs. Yeah.