Blanket assertions are often naive or simplistic, but not incoherent. They are attempts at elegant simplicity, so it's the nuanced version which is less coherent, because reality is messy.
Practical difficulties, then, can be used as an excuse for saying that an arbitrarily chosen 20% of control is vital, which is a reassuringly normal strategy, although there's no common agreement about which 20%, since this is just a performance.
The incoherence is not with itself, but rather failing to address the messy realities of the real world. Like kids wanting to satiate themselves with easy dopamine hits before having self-discipline or work ethic that makes them seek out harder things.
The 80% figure I meant is not that I think this is applicable to 80% "of learning" or something, but rather trying to convey to you that I greatly sympathize with where you seem to be coming from. I'm mostly self-taught as well, even in college my classes were basically spent reading ahead the next chapter in the textbook to occupy my interest (and doing homework due in my next class), while half-listening to the lecture to confirm what I already knew (from reading ahead the previous class).
But still I think it would be naive to assume that all kids can do without most structure.
To push people into academic crap that they hate is:
1. Pompous,
2. Counterproductive.