You can't be 100% sure.
According to studies, DHT and PGD-2 lead to hardening of the scalp tissue which becomes fibrotic and cannot support hairt grwth anymore, the follicle shrinks and dies.
So: HARDENING OF THE SCALP TISSUE!
It's clear, it can be seen on any bald man's head: in the bald spots skin is much harder, in full hair growth zones, skin is very elastic.
So, any method which can prevent skin on the scalp to get fibrotic, can be good for stopping male pattern baldness.
Who knows, maybe, after years of balding, you need to massage the scalp for hours a day, continuosult for ayear for example to get results.
This theory is so easy bashed because:
-no one has the patience to massage that much the scalp (we all want immediate results)
-hard massage leads to more shedding, and hair-loss sufferers are afraid of shedding.(even the understand well that the hairs which shed are in tellogen, and will eventually shed even if you don't touch them at all, but, we know, it's hard, when you have hair loss to apply methods which seem to push away more hair)
I don't think it isn't any truth in this theory with massaging, it is very clear to me that in the areas with thin hair scalp skin is much tight, much harder.
It is also easy to notice that balding man, in their great majority have BIG heads, looks like the head bones have grown way too big in the front and top, this aditionally puts pression on the scalp skin, keeps it tight and hard.
It is easy to see that there is minimum or no pressure at all in the scalp on sides and lower back, and scalp at the temple region and on the top of the scalp is in many cases very tight. it almost hurts if you want to "move it" a little bit.
Anyway, maybe the hurt that is done to hair follicles thorugh hardeniong of scalp tissue is irreversibe, but it is plausible that, massaging scalp daily as a preventive measure, before you loose much hair, can be good. So it is by no means a cure, but can help in prevention.
And unfortunately, when people start losing hair, they don't even think to massage agresively their scalp, they are afraid to touch it not to "lose" more hair.
Anyway, massaging your scalp you have nothing to lose. You don't pay any money, and even it doesn't regrow hair/stop hair loss, you will feel better after any massage.