Let's be mice to each other.

The comment is factual and relevant, in either case. The annoyance is entirely yours.

Agreed, I regularly make comments about how the latest "eating X shown to improve Y" study is effectively an irrelevant guide for your own behavior when it's "just shown in mice". People think they, as a human, should copy a diet that probably doesn't even work in several mice strains, and has a reasonably high chance of never working in humans. So saying "in mice" is a way of saying "maybe don't change your grocery list just yet", which is sensible.

But there's nothing in this article that purports to guide/influence the behavior of a member of the general public who wants to promote hair growth. It's just research.

Okay, many of us know this. This "in mice" should still be specified in the title.

They are still mice nonetheless.

Sure, but many of us are aware that rodent tests have flaws even when they share processes with humans: You know, things like drugs for x condition (present in both rodents and humans) is processed different in the bodies. It is prudent to remember that rodent studies are simply preliminary and often unavoidable if you want to eventually test on humans.

Hence, the request to add "in mice" to a title.

"Research causes cancer in rats", as the canard goes.