Responses

I think it's more like because Jay only does it with woman and like u say so he doesn't know about prostate (probably research it afterwards, knowing his personality) and for Yohan he must know, because he was a top (thats why he just shove it in the first time they meet even though he clearly knew it will hurt him, because that's what he want at that time) but perhaps he just thought he doesn't suit being bottom or it's not possible for him (some people is like that), because clearly he enjoys it but that's the first time Jay hit his prostate properly/intentionally
Maybe Jay really didnt know how to fuck until then! Hes only ever been with Yohan so im thinking he really didnt know how to find the prostate before so thats why Yohan was under the impression sex was just painful and a chore