The idea of Sayori being the "crazy one", having the epiphany, was something Dan Salvato considered but ended up scratching in favor of Monika having it.
However, that concept still (kind of) managed to live on in Act 4, where Sayori gets the epiphany as well!
#DDLC
MC originally had a line in narration implying that he doesn't frequent the Third-year classes
Third years in Japan are around 17-18, so for MC to not be one would imply that they're all underage!
The line got eventually changed in DDLC+ to remove that part
#DDLC