It's more useful to know the HX machine's static boiler temp than a dynamic temp reading measured in the group. By measuring dynamic brew temps at the puck, you can determine what boiler temp, and cooling flush duration, are required to give you an even temp profile at the brew temp for the shot duration you desire.
For example; in the shot shown earlier, I began with a boiler temp of 240°F, used a 5 second cooling flush, and pulled a 30 second shot at 200°F. It's that simple to pull consistent shots when you begin with a stable HX boiler temp reading.