Of course not. But it means that there is actually evidence of efficacy, even if only for select folks.
And it is those trials were efficacy is actually being tested. I.e. if they show that they work (even if only for a subset) it becomes something worthwhile to pursue.
I have a professional background in microbiology (with a current focus on infectious diseases) though I have been branching out in aspects of public health . However, I am not a medical professional (such as a dermatologist). But as a whole I am aware that hair loss related to infections is rarer than androgenic alopecia. And within the realm of infections, fungi are more common than bacterial infections. Ketoconazole, as well as other anti-dandruff components can address fungal infections, and have demonstrated relief from hair loss. Perhaps somewhat surprisingly ketoconzole was also shown to be somewhat effective for addressing androgenic hair loss, though only in a subset of people (there are also mice studies, but I am not sure whether it is clear why precisely it works, I have not followed up on that) .
But ultimately, the important bit is that there are quite a range of different mechanisms of hair loss and with associated diagnosis (though some can be related). Dermatitis related hair loss requires a different treatment than androgenic hair loss. Both again are different from certain forms of diffuse hair loss, such as telogen effluvium. To have a targeted treatment, proper diagnosis should come first.
Edit: I should add that in some studies related to androgenic alopecia folks also often found an increase in certain fungi and it has been suggested that treatment with with antifungal in addition to finasteride or minoxidil (the two components mentioned to treat androgenic hair loss) can be more effective in some patients. However, is not clear what the cause and what the effect is.