Well, that experience has really massively benefitted him.
Cause one season after his once-in-a-lifetime-wonder-season, he started 28 games in a row during which he scored 0 assisted 0.
This season, after experiencing such a brilliant start he has had 3 games, scored 0 (even despite Neves putting him through 1 vs 1 with Lloris for example - but hey, his return is only because of the crap players he shares team with, right

) and assisted 0.
Talking about sanity... you talk about progress and recent seasons, totally discarding the fact that his last season was awful. Drop back to his normal level. Literally - there is no trend - he had 1 good season and he has been crap before and after it.
In your logic - yes, if Haaland would have scored buttload of goals for 1 season and was dud before AND after it then yes - his value would be lower.