He says the reason he wouldn't do it before was entirely a legal/liability issue.
But he's also saying he'll do it now because he knows you better.
That makes no sense to me. The fact that he knows you better does not change the legal/liability issues at all.
Plus, it is notable that you are uncomfortable and worried about boundaries.

I don't know. What message does it send if a boundary can be crossed/changed because he "knows you better?" I sort of get his point. But I'm someone, because of past issues, who is very alert to boundaries breaking down. I guess my question is, why now? What, specifically, has he learned about you to change things? And what other boundaries could potentially be up for negotiation, now that you guys know each other better? It would make me nervous, too.