In most places in the UI, if someone wants to look up IP addresses for a temporary user, they will click on a "Show IP" button. Their lookup is logged.
However, on Special:Block, simply selecting a temporary user in the target field, or visiting Special:Block/<tempuser>, will perform an IP address lookup and log their activity.
While it is a smooth user experience to see IP addresses without having to click a lot, is it a concern that a user's activity might be logged in ways they didn't anticipate? (E.g. clicking on a temp user's block link by accident, or blocking a temp user without needing to look up their IP.)