Why is there a "shedding" phase when starting taking Finasteride? 1 month post op.

I started taking Finasteride a month ago, and now every day I have like around 15-20 hairs stuck in my hand. Every day. (it was way less before) Nobody reasons the shedding phase scientifically. Some say that the healthy hairs push out the unhealthy thin ones, but everyone knows that's not how hair work; they have their longer phases (anagen/telogen/catagen) Can somebody reason this DHT-blocker's effect? I would expect: No DHT = calming down of hair loss.