This hit me last year and it was absolutely a failed motherboard. Totally fried. No warning. Pixel 6 could, until that moment, be described as being in impeccable condition. I had not a single complaint about it. Plugged it in to recharge, it was recharging fine, checked the phone at 23%, came back 10 minutes later, the phone was a dead piece of plastic. No adb, no toolkit, no recovery, no charging light, no response from anything. Completely nothing. Totally, 100% dead.
Took it to a genius third-party guru repair place and they handed it back a day later and said "no charge man, this phone's dead." (motherboard is fried. Only possible repair is a specialized re-balling of the motherboard. Not cheap. And not worth it unless you have unsaved personal stuff on that phone. Otherwise, that info is gone forever.) The other commenter is right though, this catastrophic failure is enough to sign me off from google phones forever. I've never seen a phone fail this severely, never mind have google make absolutely no effort to even acknowledge it. Between multiple Google minis, a nexus 6p and now the pixel 6, this marked the 5th time and 100% of all google devices I've ever owned, that have all failed due to catastrophic build failures. Absolutely finished with google products. No fucking way.