Sure, but that's true for everything, there's nothing unique about parenting here. I.e., you similarly don't have quite the same experience as a no-kids person who has depression.

Yet this argument seems to come exclusively from parents, assigning parenthood a special status, which makes no sense, since parenting is extremely commom.

This is the same argument as “men will never understand women because to truly understand a woman, you have to be a woman” Well, empathy is quite a real thing. Also everyone’s experience is different, so even if you are a woman, you “truly don’t know what it means to be a woman”.