Is this like the opposite of an "afterglow"?
I usually feel an endorphin rush from sex, and end up in a pretty good mood. Hubby often, but not always, ends up in a bad mood within an hour. It that this?
Apparently it's not that uncommon for a negative mood to characterize the aftermath of orgasm; I've read speculation that maybe POIS is in some way an exaggerated example of a more common reaction, or at least related in some sense. Obviously I don't know how severe this bad mood is, but unless your husband is truly ill, and takes at least a couple of days to recover, he likely doesn't have POIS.
Not everyone who does have it has the same symptoms - some people get the physical symptoms more than the mental, or vice versa, some have both equally (myself among that group), but basically I'd describe it as having the flu while also being depressed, irritable, anxious and prone to mood swings.