Do they really fall of the cliff an die?

I’ve noticed that when collector was targeted outside that green platform area and my code was busy calculating something so it could not change that target in time, it went behind the right border and disappeared. It looks funny and logical, but is that expected behavior?
Can this be exploited by pushing enemy’s collectors out of the border?

Yes, they fall off the cliff and die screaming. But I think it would be almost impossible to push an enemy peon off a cliff. You’re welcome to try, though! That would totally be a valid strategy if it worked.