This is very worrying. I have two old Pixels (2 and 4) with plenty of personal data, and none have been updated for years now. I am sure other people too keep their old phones around and won't be getting updated either.
This only applies to phones who remain continuously powered on and still retain the decryption key in memory. It's possible you turn on your old, unused phone, unlock it (putting the key in memory), and plug it in for years but the number of phones in this state are probably vanishingly small.
