Don’t know about the rest, but…
Does reflashing a ROM fix it?
The phones appear to be simply dead with no response to anything. No way to connect ADB, no way to connect fastboot, nothing.
Also the bootloader allows flashing over the cable only when it’s unlocked (at least on Pixels; I couldn’t find anything relevant in the Android documentation). The vast majority of Pixels should have their bootloaders locked, and it is only possible to unlock it through the system settings, so it’s pretty safe to say that most Pixels cannot be recovered if Android fails to boot because you cannot unlock the bootloader if you can’t get into settings.
I see proofreading the first paragraph is too hard these days.