Mdd, the DC was talking about all gedolei torah in every generation, that when one learns Torah lishma, they are guided by Hashem to understand the sugya properly.
Regarding hashgocha in the Torah transmitted through gedolei yisroel, the chazon ish says the same thing about using kisvei yad of rishonim to overturn achronimc’s Torah; he says that whatever the achronim had was min hashomayim intended to be transmitted to us, and we cannot change it.
And yes, i think if a yid believes differently, it ultimately amounts to a belief that the Torah is hefker, that we’re just riding through history without hashgocha, perhaps sinning because our poskim may have erred
As for ayin panim latorah, that’s from our perspective; what was “wrong” in the eyes of one posek is because he learned the sugya differently, but to us, both are divrei elokim chaim.