This is not a problem, and sometimes happens if the device was in use, right at that moment. It's possible that a few seconds later, the command would complete without any problems. According to your esxcli storage core device list, the device is now being detected as an SSD drive (Is SSD: true). Do note that this does not make a difference for the VM's however. They still run on an SSD drive even though ESXi does not detect it as SSD.
The (only?) advantage you now have, with the device being recognised as SSD is that you can use it for swap to Host Cache.