The update button in the certificate details (added in T5903) does return "The key hasn't changed." if it does not find the key it should check. Though the key wasn't changed locally - and the statement is therefore true in a sense - a user who clicks on the update button expects to check if the key was updated externally on the keyserver or a wkd.
Easiest method to reproduce:
Turn off your network connection, then click on the update button.