System hot, ~13psi of pressure, no hose is going to collapse.
A hose collapse usually happens when a radiator cap goes bad and cannot over come vacuum (cold engine) and pull coolant back from the reservoir.
Thermostats, if installed correctly are designed to run cold, open early when they fail.
The thermal spring gets weak over time allowing it to open early with the flow of coolant.
Do check the radiator cap, make sure it's allowing the system to push and pull from the reservoir. Are you seeing excess air escaping from the system? Little bubbling in the reservoir? Is so, you may have a slight leak in a head gasket and under load you're getting exhaust gases pushed into the cooling system.