I believe there was a mistake in the guide which I think applies to you.
In the guide, where it says:
You actually don't want the Output name to be anything other than what matches the variable(s) in the script. For this guide, you would want to name the Output either ProtectionStatus, recoveryKey, or VolumeStatus. You'll notice after you create the Output, its name is a variable at the top of your script. I simply removed the already mentioned (same-named) variable from the top of Carl T's original script. The alternative to all of this is you can change the script's variable names to match your Output name but that's extra effort.
I should note that the names of custom fields can be whatever you'd like, those don't have to match anything.