I think one of my favorite thinks about LMK is that Sun Wukong genuinely feels stupid old sometimes in the sense I am genuinely unsure if he knows the difference between a 2yo, a 12yo, and a 20yo. All the characters are fully grown adults, but Sun Wukong is over here treating it like a wacky preteen adventure show because he has no clue. MK probably told him his age once and Mr. Great Sage straight blue-screened for a second doing mental calculus trying to remember what that means for mortals and he still hasn't figured it out. Old enough to be away from his parents some of the time, sure, obviously, but like...only two decades? That's not very many. How many of those do humans usually get?

When he's not tossing it on the mental pile of 'probably not important' he's trying to figure it out from context like a name you don't want to admit you forgot. This has cleared up exactly nothing.