Agreed. However, in fairness, if a person goes to the bathroom to poop then one probably will have forgotten by the time they left the room, but if instead a couple looks at each other meaningfully, excuses themselves for a bit, and then returns slightly flustered, then one will have a harder time forgetting.

As another example, if one sees a member of the attractive sex naked, then the first visceral emotional response will be to their sexiness and not to how efficiently their butt could be used for pooping.

So the analogy doesn’t quite fit, and that explains why sex-adjacent things can trigger sex parts of the brain, even when this reaction is undesired, which I think was the point of the comic–not to make some kind of grand statement about the propriety of telling people that you are trying for a baby. (And really, in the end, it is just a dumb joke, and in my opinion the slobbering detracted from the humor value so it was not executed as well as it could have been.)