This is a very important point that shouldn't be lost. We think about being bent as being a binary thing - you either take a chamber ride or you are fine. But EVERY dive involves decompression stress, and while it's hard to quantitatively measure "being tired", I wouldn't be surprised if a small amount of bubbles in the arterial circulation (i.e. CNS perfusion) was enough to cause symptoms without being enough to cause a stroke.
Remember, the PFO does not do anything to change your decompression stress. That's dependent on depth, time, mix and ascent profile. And there is a bell curve for everything, so a given level of decompression stress will cause different people to get different symptoms. There are people who blew off significant deco and never had symptoms.
PFO closure doesn't change venous side bubble formation. All it does is prevents those bubbles from bypassing the pulmonary filter and reaching the arterial side, where they can cause AGE or possibly other subclinical symptoms. For example, one theory of inner ear decompression sickness is that it's an arterial side phenomenon due to small end arteries in the ear.