Excellent question, it's not a platform at the end, it's just that I saw a facebook page, and then the description was on a site that I know but it is just a site to put people together (a foreign site I am aware of). I get it, it's not as clear cut as AirBNB but well. I suppose you are right, it does not look great.

PS: After a conversation with AMEX, it seems AMEX will consider that as a charge and could dispute it if need be.