A few things to mention here:
This is unlikely to apply to modern Pixels. This sounds like an outdated hardware issue. That notion is supported by project members who have said that this applies to devices with insecure fingerprint implementation, as opposed to Pixels and don't seem to affect any supported devices.
Furthermore, on auto reboot not helping - this presumably requires some time to setup. Aside from the fact that the auto reboot timer is configurable (with the default being 72 hours), I would recommend that people whose threat model includes anything like this being attempted on their devices to utilize the lockdown feature which prevents from biometrics from being used as an unlock method until you input your PIN/Password once more.
If you're leaving your device unattended and see anything like this as a threat; use that.
Even if this was theoretically possible on Pixels, an attacker would need to somehow bypass the lockdown feature and get the fingerprint prompt to show up while the clock towards auto reboot is ticking - how quickly that clock ticks is up to the user and their concerns.