You will see this information when you have an AP acting as Air Monitor and it collects information about wired mac on the segment or segments that AM is able to collect information on
This is to determine if you have any rogue APs connected on that segment
This one works much better :
(controller) #show ap monitor wired-mac ap-name test-ap enet-mac or gw-mac
Wired MAC Table:
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mac ip age