Not OP or an MD but in case he never answers, that was rooted in some knowledge. This particular MD seems to think that you don't need Finasteride post surgery but that is not something shared across the field.

As for the medicine it's not entirely Testosterone reducing but you're inhibiting 5a-reductase which stops the creation of Dihydrogen Testosterone (DHT), the main cause of male pattern baldness.

There is a small chance of side effects that are sexual in nature like low libido or watery semen.