there seems to be a perk cap, once you get 72/73 perks (might have been off by one and didn't feel like recounting) the perk screen flashes but then proceeds without letting you get another
also: does the dragon use different logic for anatomy selection? because i have it set to 10/10/69/10 but have always got the one for the dragon
I was able to get a male dragon to show up once, but I couldn't tell you what made it happen. It's likely it prefers traditional lady anatomy, but it does conform to preferences to some degree. In my efforts, getting a flat-chested dragon with a peen took setting my preferences to encounter only flat-chested monsters with peens, but not knowing what's going on under the hood makes it difficult to know if that's outright required.
Edit: Thanks to the first dragon I encountered since making this statement, I can confirm that the pigeonholing I resorted to before isn't necessary for the dragon's anatomy to vary.