The metal palms and soles of the suit mean it's definitely not Kaine. He was also well known as his Scarlet Spider identity and even part of the New Warriors, if he needed to fill-in for Spiderman he would just come as himself, he doesn't need a disguise.
My guess is Norman, Kaine isn't a genius the way Ben/Jackal, Peter, or Norman are and they draw attention to this new edgy web shooter formula that's impaling people and takes hours to dissolve and needs to be cut apart with power tools.

Kaine very much DOESN'T want to be seen as Peter and is the most independent of the clones, Ben being a creepy stalker impersonating Peter at his job and to his girlfriends is in character but Kaine doesn't want to NTR peter's life from him, he wants to chill on a beach sipping margaritas.