If they're in series the pressure will increase, if they're in parallel the flow would increase. Just have a pacemaker organ connected to both to time the pumps. You could reduce blood pressure but increase the amount of blood flowing, therefore less wear and tear on the hearts, arteries, organs, etc.
It's the human equivalent of when dogs want you to throw the ball without taking it from their mouth. People need to exit to make room for people to enter.
The worst are people who do that in the bathroom. Like, hello, I'm trying to jerk off in peace here, stop polluting the air with your banal conversation.
Full metal jacket is a fantastic movie, but not really an example of inclusivity. A later line goes:
"Only steers and queers come from Texas, Private Cowboy, and you don't look much like a steer to me, so that kinda narrows it down. Do you suck dicks?
Sir, no, sir!
Are you a peter puffer?
Sir, no, sir!
I bet you're the kind of guy who would fuck a person in the ass and not even have the goddamn common courtesy to give him a reach-around. I'll be watching you!"
So the succubi creates a session with no scheduling conflicts, wow that would be hard to resist.