All video cards have the potential to throttle. Just need to hit the right (wrong) combination of ambient temps, case temps, loads, airflow and bang you got a hot card.
Picture: 200mm fans are Great for moving air, but suck at making it move, very little static pressure compared to a much smaller fan. That was the biggest complaint of the original H500 cases, that solid front and low sp fans. That's why later designs included a Mesh front, the glass front was starving the case for airflow.
80°F is 27°C. That's exterior ambient. Everything inside the case is starting with a 27° base temp. Add in Sata chipsets, USB chipsets, VRM's, gpu, cpu pump, tubing, drives and every other source of radiated heat and the lousy airflow and the interior of your case is approaching or exceeding 40°C.
If the load on the gpu is sufficient to create a larger Delta, added onto the 40° case ambient temp start, you get a cyclic airflow pattern, the case temps rise as more heat is produced than can be expelled. That's when you see throttling temps. You basically turn your case into a convection oven.
In a case with good airflow (that doesn't mean More fans) the heat is expelled as fast as its produced, no cyclic pattern, load temps are what they are.
Best case scenario is mesh front, higher set fan curves for both intake and exhaust fans, case next to open window. Get the heat out of the case and it cannot be reused to try and cool the gpu.