I'm not too sure that the CPU PLL OC has anything to do with temperature sensor settings or voltage to them...it's the voltage used to create the clock that the CPU runs at, not the voltage required to perform any tasks. It's also suggested to bump it up a bit when doing higher overclocks, and it definitely has a minimum when it comes to stability at certain clocks on that chip. In my MSI Z270 Gaming M7's BIOS, the setting has a range of 0.6000 to 2.0000, and defaults to 1.2000. I've also read that not all boards default to the same voltage either. When testing with my i7-7700K @ 4.8GHz, I was hitting ~86C with a 240 AIO. But after some testing, I found that the lowest my chip was stable was with the PLL OC set to 1.0500. 0.9000 wouldn't even boot, while 1.0000 booted, but was unresponsive once at the desktop. But with the 1.0500, my temps dropped from ~86C to ~67C after an hour of Cinebench R20 without an AVX offset. That's at 4.8GHz...5GHz needed at least 1.1000 to boot, and I'm still playing with it for stability. I just delided Thursday and have been having some fun.
Personally, I don't see them adding a feature that would potentially give the user a false sense of security due to incorrect temperature readings. And if it was so dangerous, you'd think they'd have a big warning about it in the 'help' text of the BIOS. The core temps drop considerably, but the wattage used by the chip is the same, which is why most seem to think the readings are skewed. But...although the cores dropped by ~19C, the CPU's GT Cores only dropped by ~4C. The GT Cores are on the same chip, so if the CPU's cores are ~19C cooler, then shouldn't the GT Cores also see the same ~19C drop if the temps were skewed?