Well, this is true, but all the swelling that goes on during a heat cycle it definitely part of what allows a male to make his mark. They don't seem to have particularly good aim. :lol-sign: And the vast majority of spayed female aren't going to stand to be penetrated - it would be very uncomfortable, I'd guess, as bitches who ARE in heat and are willing still often find it to be somewhat distressing at times.
I'd say it's possible but fairly unlikely, but that's just my educated guess.