The argument goes, "His bangs went up, therefore he turned SS2"
It's cap, because we saw Goku's bangs get erected like that when he powered up earlier in the episode:
No reason he'd turn SS2 just to stop himself from rolling over. His bangs only went up for an instant here, but that was...
I was drawn into it because of how it looks so much like early DBZ's art style; I'm almost surprised it wasn't animated by Toei. Needless to say, Toriyama designed the characters. Anyway, it's a pretty shit anime; I just skimmed through it.