First thing I noticed is 821 hours flown by PM in previous 12 month and its a lot for this kind of airplane and environment. With short legs and routine predictability you are using muscle memory instead of brain. Probably they were both looking outside to find new runway and were in a rush. So when he accidentally grabbed condition levers his hands played trick on him and feathered props without him noticing - yes, both levers are protected by a mechanical lock but its a simple spring lift switch. It would be interesting to see their post landing SOP's to find out who and when feathers props on a parking stand and if they have a callout for that. In my airline only captain had a tiller and he would taxi to stand and then feather both engines without a callout, but later is was changed when they introduced one engine taxi.