I've studied and taught Shakespeare, and been professionally acquainted with Shakespeare scholars whose names (at least) other Shakespeare scholars know. That's an... eccentric reading. There's no "definitely" in literature, of course, and GP's reading can be made to work.

If I were to try to defend it in an academic setting I'd be looking for how securely or inevitably "groan" is used as a synecdoche for orgasm (I can think of at least three instances in Shakespeare where it doesn't, and off the top of my head no others where it does), and for other period instances where the neck is eroticized as a site of ejaculation (I am not aware of any).