From the blog about adventure packs.
(Remember that the PACS Guide requires that any specific cards listed on the back of your character card must be in your deck, so if Helen gives up the Ultimate Combat deck, she would still keep Hayato’s cohort Jinfu from that deck.)
From the back of Ukuja's character card.
Cohort: Each scenario, choose 2 Hunter Class Deck cohorts
Not a named Cohort but I doubt it is the intent to strip all hunters not named Adowyn from using cohorts.
In what sense is “2 Hunter Class Deck cohorts” not telling you about specific cards? That seems pretty specific to me.
I'm not sure I agree, RAW. It certainly doesn't name a Cohort or a card; it tells you to pick from a pool of possibilities.
For example, if your favored card type is a "Sword Weapon", is every Sword Weapon (which is also a pool of cards) "specific" cards that will be taken from your 'initial' class deck even if you use three weaponless Adventure Packs instead?
I certainly agree RAI Witches and Hunters should keep their Cohort choices even if they use an all-Adventure-Pack setup, but I'm not sure the wording of the guide supports that interpretation. Happy to be convinced that it actually does, though.
Also, for reference, these are the actual rules listed in the Card Guild Guide (the OP only listed a paraphrased, non-binding blog post reference to them).
All of the cards in your character’s Class Deck box must come from your Class Deck, with the following exceptions.[...]
• If the back of your character card names a card such as a cohort, you may replace that card with any other card that has the same name and type.
• If the back of your character card lists a specific card, that card must be in your deck.
Whilst not immediately relevant to the discussion, the fact that Ukuja clearly doesn't NAME a Cohort means he could not possibly use the WotR version of Leryn, whilst the Hunter CD Adowyn could, as per the first dot point.
RAW, I still don't think "Any two <X card type> from <Y deck>" really fits the bill of "a specific card", though.