That said, it's definitely very frustrating as someone who does the occasional server build. Not only does TDP not reflect minimum or maximum power draw for a CPU package itself, but it's also completely divorced from power draw for the chipset(s), NICs, BMCs (ugh), etc, not to mention how the vendor BIOS/firmware throttles everything, and so TDP can be wildly different from power draw at the outlet. The past 5 years have kind of sucked for homelab builders. The Xeon E3 years were probably peak CPU and full-system power efficiency when accounting for long idle times. Can you get there with modern AMD and Intel chips? Maybe. Depends on who you ask and when. Even with identical CPUs, differences in motherboard vendor, BIOS settings, and even kernel can result in drastically different (as in 2-3x) reported idle power draw.
But they don’t use real temperatures from real systems. They just make up a different set of temperatures for each CPU that they sell, so that the TDP comes out to the number that they want. The formula doesn’t even mean anything, in real physical terms.
I agree that predicting power usage is far more difficult than it should be. The real power usage of the CPU is dependent on the temperature too, since the colder you can make the CPU the more power it will voluntarily use (it just raises the clock multiplier until it measures the temperature of the CPU rising without leveling off). And as you said there are a bunch of other factors as well.
Are you just describing product segmentation? ie. how the ryzen 5700x and 5800x are basically the same chip, down to the number of enabled cores, except for clocks and power limit ("TDP")?
