Okay hear me out for a sec, but I believe Drampa may be evolved from a split evolution.
Now you may be wondering "lol but why anon?" well think about it.

Drampa is obviously derived from "Dragon + Grandpa" therefore it must be a male only mon with a name like that.
The fact that it LOOKS like a final evo makes me think that there might be a middle stage before it and then the first stage that splits.

My theory is that if it is a part of a split stage evo it'll look like this.

->1st stage: child like dragon pokemon with the ratio of 50% male or female in the wild
->2nd stage(s): adult like dragons, one a male only species and the other female only. Both split from the child stage.
->Final stage(s): 2 elderly dragons with the "grand" names worked into theirs
------->Drampa
------->Dragma (speculated name)

What do you think?