I’m sure that many people would consider the example I quoted (“Almost invariably, if the group was mixed, someone, almost always male, would try to "correct" our gender-neutral greeting.”) a “mansplaining” micro-aggression.

Consider your own example “highlighting gender by singling women out in a group of men (i.e., “Hey guys, and one gal”)”

Don’t you think that some people would see there a “invisibilization” micro-aggression if “Hey guys” had been used instead?