I entirely agree with your point of view.
I would say in this case it would be not higher that a 10% chance that the pepper-spray would have something to do with the deaths.
As far as I know, it's just a concentrate from chili peppers, although it does have an irritating effect in the lungs/eyes of humans and dogs, mostlz giving us the feeling it burns (believe me, it does burn
) I believe scorpions can tolerate it without major problems, and I doubt it has something that would actually be toxic to them.
My german sucks these days, but the can says "Mit natürlichem hochaggressivem pfefferkonzentrat"