是否有任何方法可以从过度编写的Android系统恢复中恢复，或者还有什么可能导致像素XL不会从恢复进入FastBoot？ -- fastboot 领域 和 boot 领域 和 bootloader 领域 和 bootloader-lock 领域 android 相关 的问题

This is an attempt to sideload an update to a Google Pixel XL stuck in a boot loop.
Following this answer from the official Google forums, I tried this procedure as linked in the chosen answer. Unfortunately at step 9 it states:

9. You will see the Google logo for a few seconds followed by a green android on his back with xe2x80x9cNo commandxe2x80x9d underneath. Press and hold Power, then tap Volume Up once, then release Power.    NOTE: If your device starts rebooting at this point, your only recourse is to contact your place of purchase about a warranty replacement or repair. 

Unfortunately, sure enough - the device starts rebooting. This Pixel was bought by the previous owner from Verizon and I'd wager ten of them that they want nothing to do with repairing the phone, and would happily sell the user a replacement.
I don't understand what state the android on his back visual indicates, but I believe that the subsequent state would be the android system recovery. If the system is failing to enter that state and instead continuing to boot, it seems to indicate that a symlink or other direction or storage block has been over written. Is that true? And if so, is there any other way to enter android system recovery and continue to step 10 of the above-mentioned instructions?

For context: the user had started noticing battery/reboot/bootloop issues a few days before the device finally rebooted on its own and failed to completely start.
In trying to start the device normally, occasionally the boot loop will get far enough to spin the dots and display the "G" and powered by android at the bottom of the screen. It essentially always reboots after that to the Google splash that appears during initial boot-up.

For insanity's sake: Is there a way to JTAG into this thing?

Edit to add debugging info

user@host:~$ fastboot flashing get_unlock_ability ... (bootloader)    get_unlock_ability: 0 OKAY [  0.052s] finished. total time: 0.052s user@host:~$