This part on no class bonus is still true. It just means you’d get neutral and the class‘ cards on an equal possibility. But sorry you’d have to Google it, it was less than 6 months ago.
If your class does not have the type of card being discovered (in this case Secrets), the card uses its own class. For instance if a Shaman using Underbelly Angler gets a Hydrologist and plays it, the Shaman will be offered a choice between 3 Paladin Secrets.