The principle of overwhelming strength trumping all techniques applied everywhere. In actual combat, powerful physical abilities were unquestionably more important than powerful techniques. And Saitama's physical abilities... Whether he had technique or not, he could settle anyone with one punch. If he encountered someone like Boros who could not be blown apart with a single punch, the most they could do was tear off his clothes. Then he could just follow up with a Serious Punch. Technique truly made no difference to him.