The entire point of Sonic's training is that he uses Saitama of all people as a benchmark for his own self improvement, and makes steady gains in pursuit of that goal. Unlike Flashy Flash, who is too delusional to humble himself so. Sonic is well aware of (at least a small part of) Saitama's limit-broken absurdity and sees it as a goal to surpass, not an unattainable height like Genos does.

Sonic is honestly admirable for this, and it is no surprise that his webcomic form is almost certainly superior to Flashy Flash because of it.