I always figured there’s some kind of Force time dilation going on on Dagobah that allowed Luke to experience more time there than Han and Leia did in the Falcon. They later used that idea explicitly on TCW, and I think the implication in TLJ is that Ahch-To is the same way. I think the idea that time works differently in certain Force-strong places is almost certainly a retcon they cooked up to make sense out of ESB after the fact rather than something they were thinking about while making the movie, but it works for me as an explanation.