[Formulajones]

If you have a good cooling system that works like it should and an engine that is happy with it's combo of parts and tune, it's not unusual at all to have an engine run below the rated thermostat temp. Especially if ambient temps are relatively cool outside (90 and below)
Reason being is thermostats open before their rated temps. Sometimes as much as 8-10 degrees earlier as a starting point, and if your engine is happy and the cooling system is up to par, many times just that crack open temp on the stat is enough to keep things cool.

I see this as perfectly normal. If the temps bother you then you may just have to experiment with warmer thermostats and see if their open temps are what you're looking for. They all aren't created equal so it may take a couple tries.