I may need to reread but I recall interpretating it as "looney-tunes" logic where the rule is "defeat in one punch" and that he broke his personal "limiter" despite the somewhat normal regiment (gotta respect that 10k run everyday).

Everyones got different limiters (Garou I think is the closest other example we have) but the sheer work needed to break a limiter is described as ridiculous. It shows how average Saitama begun as and how seriously he took the training to do that everyday.