Over on the ST Community, a user found $name and $currentEventDelay were being added to the query string with a GET request. The wanted part of the query string was actually being specified in the URI so when the piston was being viewed or edited there was no indication that variables would be used (i.e. it didn’t say ‘with query variables’ or whatever the precise wording is).
I had a play and discovered that if you add some variables to the ‘Send Variables’ section, and then change your mind and switch back to ‘Nothing Selected’, the variables will remain in the request. They have to be explicitly deleted.