Boros was the strongest opponent Saitama had faced. The one and only foe, especially at the time, to come even remotely close to giving Saitama a good fight. He could surprise Saitama, impress him, debatably even slightly harm him, and make him get serious. He was a parallel to Saitama, someone who became so strong that no one could face them, and because of that, he suffered from boredom. But eventually, he came to Earth, and found someone who suffered from the same kind of boredom. Boros managed to finally reach his goal of finding an opponent who can match him, although in the end he realized he never had a chance, but unfortunately for Saitama, he was still unable to truly have a good fight, to truly use his strength to the fullest. Honestly, I doubt Saitama is even more than a thousand, maybe not even a hundred times stronger than Boros.
Even with this new feat, I'd wager that ONE and Murata view Boros as capable of beating Orochi even without Meteoric Burst.