Mysterio is here pretending to be Spidey; the scene has a double meaning, because it's not only letting Flash fulfil the fantasy of his hero finally striking back against his stereotyped idea of nasty ol' Jonah, but the Mysterio of the time was yet another of Jonah's former hired supervillains, and had some (never fully explained) emotional connection to Jonah's wife Marla. This isn't Spidey striking back, sadly; it's some geezer named Daniel Berkhart.
I'd suggest the next moment from the issue should be the one with Gwen & Peter in the ambulance. (Reply to this)