On the Assets> Devices > Devices by Serial Number page, it presents a checkbox next to every individual device instance (by serial number). Checking the box and clicking Action > Globally approve misleadingly approves every single device with the same name and vendor. Additionally even if it approves multiple devices, it states "globally approve succeeded for 1 item(s).
Issue tracked under engineering ticket CRE-21095
This will be fixed in the upcoming 8.14.x release. Workaround is to go into the device details and click "Approve Serial Number".