Deku_Hero_5330

can't he solve the flaws himself as he is already working on making a technique that retains only essence and removes flaws to make the ultimate technique.

Can he absorb the sun qi (which is too strong for him directly) by practicing in water and increase the time period for it?

may be the real upgrade happens when it reaches perfection, so it's like plot armour for mc as no one other than mc can reach it without subsequent method.