Mightyena Ability Bug

[Fallen Angel]

Hello; today I catched a Poochyena with Rattled ability, and I lvled it to lvl 30. When I evolved it, it kept its ability. But when I checked PokéDex I saw that Mightyena can have one of the following abilities; Intimidate, Quick Feet, Moxie.

 

[Sheeper]

afaik inheriting an ability from pokemon's pre-evo is possible after evolving, even if the evolved form can't learn this ability on it's own.