I've been having NEs almost all my adult life, and more frequently now that I'm avoiding anything that could end with an ejaculation, and they have never given me POIS symptoms.
I associate this behaviour to the fact that when I have a NE I don't have an erection, and the flow of blood is very much reduced on that region in comparison to a normal ejaculation.
I'm almost sure that my POIS is a consequence of some kind of allergy to my semen, as I'm allergic to several things and I find similarities… although with POIS the consequences are much more severe and can't be avoided by just taking an antihistamine.
To confirm a little more my theory, a couple of nights ago I almost had a NE, but I woke up and could contain it, so I just ejaculate a very small part, but I started to have a little itching inside my penis, but luckily with no other consequences.
I wonder if those of you that have POIS symptoms, after having a NE, could confirm if you have (or not) an erection during it.