This isnt RH, it's literally what happens for some when finasteride starts to work. Some are mild sides, but the shedding at 3 months is right on schedule for the drug working. You get a increase in T (acne, body hair) and some temporary shedding, gyno is the opposite effect. I know this for a fact because I actually got RH after restarting finasteride, and let me tell you it's a lot different then you are describing. My scalp was soaked, red, had acne and painful everyday, I lost hair by the handful.
I shed from month 3-9, recovered a bit then maintained for 6 years. Ran out and couldnt resupply due to covid and got fucked up.