When using Fly and you’re knocked out, do you fall?

I was running my game today and came across a situation which got the group into a heated debate. What happened was the witch was flying along using their fly hex 20 feet up in the air and got knocked out due to damage.

The players were arguing that the spell was no longer active and thus the feather fall aspect of fly would kick in and no fall damage. They even argued that it would behave similar to air walk and they would be resting in the air. Despite the spell/hex having a duration, and not a concentration. I ruled that since flying requires concentration similar to walking, and you fall down when you are knocked out, and thus you fall. The fly is still in effect however.

Please confirm or deny that my interpretation of the rules is correct. I like having 3rd party confirmation when making rulings on things.