hahahaha this is so funny you guys never give up.
this is assuming that the association knows EXACTLY how strong the heroes are, and the association CLEARLY DOESN'T.
King is only considered to be the strongest man for never showing any signal of fear, no signal of fadigue, no signal of ''hard work''. Even for the association, he's featless and considered a ''unknown being''.
About Orochi, none but SAITAMA HIMSELF saw orochi's full potential, actually, the association never met Orochi in the first place, but had informations about him.
Tatsumaki was considered island level+ until chapter 132, so any scaling made by hero association is useless, without mentioning that psyko's godblast was barely noticed by the humans, was just a REALLY BIG explosion with immensurable energy, genos supports this.