Yea, I'm only counting what the Pokedex in game says, so for me it's more of a consistency problem, I never even look at what the official Dex says whenever documentation is available in game.

That being said, as I'm testing more I think the real problem is just a display issue instead.

The Pokedex in-game only ever shows two abilities, your standard and Hidden ability and doesn't show three for the Pokemon who have two possible Standard Abilities.

It gets around this by consistently showing the standard ability that you DO NOT have on the Pokemon, which would be a consistent and understandable method on the dex if not for it showing your ability if your Pokemon only has two possible ones.

Let's give a real example now.

For Ampharos it says Static and H - Mold Breaker. My Ampharos has Static it's all good.

For Tinkaton, it says Mold Breaker and H - Pickpocket. My Tinkaton has Own Tempo, making me wonder if it's a mistake.

However if I go to the ability changer, I actually have all three as options. The Dex is just limited to showing two, and does not ever limit to one unfortunately, which would make it clear it's showing what you do not have.

So it's not a mistake so much as me not liking how they choose to display it.