The fix required you to download and flash a few modified system image files which circumvent the bootloop by disabling the larger CPU cluster.
Last year, users of the Google Nexus 6P and Nexus 5X started reporting cases where their phones would enter a bootloop and thus refuse to boot, something that effectively rendered the devices unusable. This was different, and while reduced battery life is certainly bad, the bootloops essentially turned the smartphone into paperweight. Unfortunately, Google and Huawei were not listening to these complaints aside from replacing units under warranty. The instructions on how to go about fixing your Nexus 6P can be found on the XDA forums, posted courtesy of XDA member XCnathan32. The SD810 is configured in big.LITTLE configuration - with four ARM A57 cores as the high performance cluster together with four A53 cores as the more energy efficient but slower cluster. As it is, the high-performance A57 cores are the ones responsible for the bootloop issue on both phones and once they are disabled, the phone works perfectly.
It's not that hard to get things going with the new solutions. No amount of flashing and wiping fixed the issue, so it was clearly a hardware issue. Be sure to let us know what your experience is in your comments below.