From many years of experience on GO trains, I've seen these accidental alarm calls many times and it's really a continuing phenomenon, though most notably outside of rush hour, but I don't think there's any more than usual now.
The most common misuse I've seen is always passengers who wake up at the last moment and realise they are about to miss the doors closing at their stop and think that pressing the alarm will keep them open long enough to get out of the train, and this actually does work sometimes.
I've also seen this on the Niagara express trains where people press it to try and force the train to stop at a station that would normally be skipped, which of course doesn't work. Interestingly, I was once on one of those Niagara trains sitting in the CSA car which did made an unscheduled stop at Appleby, and it was because a group of clearly confused first time passengers very politely explained their situation to the CSA who then asked control for permission to stop there, and it was granted.