Well, I think they should actually show us both values.
First, they could show an ambient range for your model, with marker for your current temperature. That would at least give users an idea if they were out of bounds or not–another question we see daily here.
Glowforge Pro (70F)
They could add another pip or another thermometer bar that represented coolant. The temperature values for the coolant are probably not meaningful to us, but they could find simple graphical way a way to show us if the cooling was keeping up or not, and how long a cool-off requires, once initiated.
I understand their desire to make the device easy to operate but I think they hide way, way too much information from us.