@zergio200ism best explanation is, he is strong but only in certain aspects
for the INCREDIBLE long timespan he trained, he never actualy trained against anyone but himself, making his training incredible lopsided and unbalanced(the best training is and will always be against someone else), he is strong by sheer muscle memory and "experience" but if it comes to actual technique against someone who knows how to read an opponent and counter, he is extremly week , because he never had to deal with anyone like that in his training.
Take a cook who, for all his life only ever learned how to properly prepare egg dishes, he never learned anything else. Now Task him to prepare a Steak with some fancy sauce(not realy a steak eater myself so shallow explanation)sure, some of his experience form preparing egg dishses will carry over, but the crucial parts, aka how to prepare a proper steak, wont.
i am almsot 100% sure that it wont matter for the MC in the end tho