Perhaps they measured the temperature of the espresso shot post extraction, in the cup (or more formal receptacle!), where it would be cooler than the water meeting the ground coffee.
Also, a Gaggia Classic (as an example - they don’t specify which model they use) does not have a PID. Temperature of the espresso leaving the group head drops during the extraction.
Also, a Gaggia Classic (as an example - they don’t specify which model they use) does not have a PID. Temperature of the espresso leaving the group head drops during the extraction.