You might be right. My thinking was this: peak cylinder pressure basically is proportional to torque, so at lower power levels cylinder pressure is overall low

You might be right. My thinking was this: peak cylinder pressure basically is proportional to torque, so at lower power levels cylinder pressure is overall lower. Even if the engine knocks, which will cause a spike in cylinder pressure, it starts from a much lower baseline, and there's also much less air/fuel mixture in there. Thus peak cylinder pressure for a knocking engine at low torque may not be much larger than that of a non-knocking engine at full power. But this is just speculation on my part, I don't have quantitative data. It's also possible that it is the sharp pressure spikes that do the damage rather than the overall pressure level, in which case what I'm saying would be less applicable.