I just thought of something. When Luke and friends are on the skiff, and he tells Han, “there’s nothing to see, I used to live here, you know” doesn’t Han know what Tatooine looks like? He’s hung out there before, in the first movie.
I’ve rationalized this to say that sure, he’s been to Mos Eisley, but hot the “middle-of-nowhere” parts like the endless sand dunes where Luke’s home was. (I don’t want there to be an issue with this line exchange because I love it)
Yeah I’m pretty sure your rationalization is the correct answer here