> I would expect this OR-condition to either pick all of the instances that are to the left of X=500, or pick all of the instances that are above Y=500. Even as we're talking about this, I struggle to think of what else it could logically do.
You say it should be one or the other, so which would your actions apply to? It makes sense to me that sprites that meet either criteria would be picked for actions to happen.
Exactly, the use of 'either' doesn't make sense in the context of how Construct is picking instances and applying actions to them. It will pick all the instances that meet at least one of the conditions.