That seems spot on to me. When you lower the temps, the GPU cannot sustain full utilization as long until it has to throttle to lower the temps back down.
In most cases, CPU and GPUs will ramp up to 100% bc the temps are still low. As the temps increase at 100%, then the GPU has to scale down to keep the temps at what you set.
Think about it like a car engine. If it overheats, it needs time to cool down before ramping up again.