I don't think this is true beyond benchmarks. They stress test the CPU and that's when the throttling hits the hardest. It's throttling peaks in CPU usage, and a benchmark is all peak.

So this sounds like a worst case scenario. Actual use can be completely different.

Not defending Apple though. This complete lack of communication over an obviously controversial choice is amateurish. So much of this could have been easily avoided by clearly mentioning it in a Beta release, along with of course implmenting an on/off switch!