I've been wondering the same thing. I saw a small study (which I wasn't able to find today) suggesting finasteride helps quite significantly post-surgery with survival of grafts.
If finasteride has nothing to do with survival of grafts however, then we can probably go by how aggressive your hairloss is. Mine from age 17-30 is slow, so I might risk it.
And maybe I haven't seen bad results to go by, but hairline is always the most important to your appearance. If you lose more at the crown later on but still have a good hairline, it won't destroy your appearance overall. I do understand the hypothetical scenario of losing behind the hairline, but if you keep your hair a bit longer that wouldn't be disastrous either. Again, still better than egghead frontal view.