>>28057558>>28057497In the case of Skarmory only one trainer used it in the entirety of Gen 2 and he was a post game trainer. So there's an extremely low chance of seeing it in the main game.
Slugma was another common one who only had one trainer and it didn't appear until you rematched them if I remember right. Anyway despite being found in three different routes it still had a 5% encounter rate.
As for Gen 3 however multiple trainers have them including several hard to pass trainers, gym leaders and even the champion.
They just had more of a presence in gen 3.
There's a reason people say the distribution is bad guys.
