Seem like my theory was correct. Bypassing the heater and not capping the pipes will send hot coolant to the bottom part of the block to blend with colder coolant.
In the oem configuration, having the heater will lead to a cooler effect even if there is no air flow going through it
As you can see the inside cavity of the thermostat where the hoses go are only divided by a small piece of aluminum, this is so the heater change in temp doesnt affect thermostat operation. These cars do not bring a heater flow valve meaning coolant is constantly running through the core and it's the blend doors job to block airflow so you dont get hot air.
Time will tell however I wonder for those experiencing high coolant temps while racing if they'll see a significant improvement in coolant temps by shutting flow to the heater all together.