There are more reason for card to throttle. even if you can keep it at 45°C, it still can throttle once power limit in vBIOS is reached. My HD7970 was throttling a lot in experiments with TDP as I lowered it to 175W. That means reviewers could have card(s) which needed more juice for given clock than allowed. And different kind of workloads put different load on GPU even if each shows same 100% utilization. (One of reasons why review sited show sometimes quite different power consumption.) But TDP throttling has simple solution, people just have to allow higher TDP limit and who cares if it eats 25/50W more.