CPU_CYCLES counts cycles. This means that the time per cycle varies with frequency. If you're trying to see how many cycles something that fits in L1 takes, CPU_CYCLES is the right thing to measure.
Parent is pointing to documentation suggesting that it's measuring time and dividing it by frequency, and perhaps not perfectly in the case of dynamic scaling. They seem aware of what CPU_CYCLES is supposed to do.
The documentation is not the best. CPU_CYCLES is genuinely counting cycles.
perf is all about reading actual hardware counters. It's awesome for this. There is essentially nothing made up about perf's output, except to the extent that the hardware itself reports inexact output. (For example, perf annotate may attribute events to an instruction near the instruction in question on older hardware, because older hardware has a small amount of skew when sampling.)
