To be frank, most things do nothing even when they do reach the follicle, statistically speaking, so I don't think that's a good measure of effectiveness or the major reason why something doesn't work.
Generally, for reasonably small molecules that are soluble in ethanol, the vast majority of them do not need a more fancy vehicle than that to be used topically. Some people may have a more or less porous or vascularized scalp which can affect systemic distribution and absorption, in which case you either use a higher or lesser concentration of the compound.
Of course, with anti-androgens, if you try some abysmally high concentration and it still doesn't do anything, chances are, maybe you have some kind of mutant receptors and this class of drugs simply won't work for you.
The commonly effective dose range for RU is 50-75 mg. I couldn't fully stop my hair loss even with 100 mg (fairly high dose) and at that point I was already getting systemic side effects. Hence, I can't possibly imagine 250 mg being a safe long term dose, even if it works.
People who need such high doses of conventional anti-androgens should best switch to AR degraders as soon as available, I can see that being safer and more effective at smaller doses.