Earlier quoted context omitted.
This is really interesting. Clearly they're trying to control for sensitive variables that make little sense even to them, and yet they're still using rodents as subjects and publishing studies likely without mention of these oddities. Not saying everyone is doing it wrong, but wow.
You have to allow for some level of pragmatism. They found a method that seems to provide better data without actively biasing their results. Rodents make convenient test subjects, and no scientist wants (or more likely it doesn't even occur to them) to include an unproven methodology in their published work.
Or do they just publish, "X caused effect Y"?
Frankly, identifying why it requires a female, or female non-cat owner sounds like it may be more interesting than whatever other result they are working on...