I actually didn't know about his schizoaffective disorder back then although I did hear he was bipolar (really I don't know much about the real life details of Beach Boys outside listening to their music). However when I saw Brian Wilson walking on stage, I notice him having shuffling/Parkinson like gait/movement and his face was pretty much blank with no emotional reactivity.

I was thinking, geez he looks like someone who has been on antipsychotic a bit too long and someone with negative symptoms of schizophrenia which now makes a fair amount of sense.