If you go back to what I originally said, the actor's role is unchanged. They are essentially acting the same role they would do anyway, but being observed by two conga lines instead. They are still doing the same thing they would do if it were 1 conga line. In my example of Stranger Things, the same Eddie SA will do the same thing he did, the difference is that two conga lines diverge into his scene, view the same set of action but on opposite sides, before splitting away from each other again. Not asking them to do double the work. Same work, gain the benefit of two observers.
FYI - I've mentioned in past discussions that HHN needs to find a way to hire more SAs (or something else entirely) in order to alleviate the workload. It's evident that there's a drop off later on in the event with empty boo holes, resulting in a negative experience for later guests.