How would a settlement with the Authors' Guild cover orphan works? If the Authors' Guild is in a position to grant a license, then it's not an orphan work. The whole orphan works problem is that for a lot of valueless works, nobody knows who owns what.
Class actions can include people just by describing who makes up the class, that’s why the parties who worked on the proposed settlement came up with the plan. This method (uniquely) allowed settling with (essentially negotiating a deal with) all those unknown parties, a feat impossible otherwise.
The class as I understand it was the copyright holders of every book in a library, and if approved by the court they can all be legally said to have agreed to the settlement’s terms if they didn’t opt out. Now as with anything legal the whole thing depends on someone’s interpretation of whether it’s ok, but this was a plausible reading of Rule 23 of the Federal Rules of Civil Procedure.
One could file a class action suit on behalf of everyone who ordered a strawberry shake at a McDonald’s in 2023, without ever knowing who or exactly how many they are, and if a judge certified it as a class action and McDonalds cut a deal with those representing the class, the terms would bind them all (except those who explicitly excluded themselves).