Not really. Flash came after Geryuganshoop, so it’s a lot more reasonable to scale him (even though I think that scaling isn’t super solid either) than it is to scale Boros to Orochi because of statements made before Orochi even existed in the story.
Especially when you consider that we accept Saitama growing strong enough to
completely outshine his strength from the day before, so what Saitama considers to be “strong” in the Alien Conqueror Arc can’t be compared to what he considers strong in the Monster Association Arc. Oh yeah, and Saitama treated Awakened Garou, a
Tier 5/Tier 4 character, as
more of a nuisance than anything, so the reasoning of “Boros scales because he called him strong“ is still faulty.