By the rest of the series, he meant everything outside of Saitama's power origin, which technically includes Saitama's interactions with all the characters. So no, you don't really agree with him.

And I quote: "The only outlier is Saitama's power's origin."

And there are more than "a couple extra gag characters." There are tons of them, and even the more normal ones all behave intentionally exaggerated as parody. Look at Genos, arguably one of the most normal characters, for example. How is his density and absurd seriousness supposed to be taken seriously?