Everyone who rides goes through this new queue entrance. Only the non-riders go in directly through the gates (the right half of the path through the gates). Then once you enter the cliffs/dungeon, there's staff directing people with bags to the lockers, single riders to the left, etc. So if you ride you must enter through the new extension, no matter if you are a single rider, a party of 2+, have or don't have bags.
Here's a rough sketch I just quickly dribbled to show how this works: