Just to clarify, acetyl propionyl is a diacetyl substitute, one that some seek to avoid inhaling. It's a buttery flavor.
Acetyl pyrazine is not a diacetyl sub. It's a grain-y flavor.
I've seen both referred to as "ap". I'm sure this flavoring has acetoin, acetyl propionyl, or both. Capella does say they don't add diacetyl. If they have or release a "v2" of this flavor, it'd probably use butyric acid instead, like their other v2s.
@Dixie1954 is the expert acetyl pyrazine detector, so if she tastes it, I'm sure it's there.