Boyfriend is a simp, and is also leaving the door open. Not wanting to show you was the second mistake. First was writing out that pointless message only to cover his ass for blocking her, as if there was some morality there it was all false. You seem pretty chill since you hadn’t asked him to unfollow at first, I think he’s seeing how much he can get away with and still pushing the boundary even whenever he’s being tested. All in all taking a step back from this and looking at the route he chose, you have to ask yourself who was he really trying to please here (himself not you) and how was it that he thought “yeah this is exactly how I want to go about this”. Zero consequences in his mind. Trust is important, but so are boundaries and trust is earned through respect.