Post title seems a bit disingenuous when you have already gotten an official response clearly refuting the update being the cause.
GrapheneOS That appears to be a hardware failure. Updates are fully validating by reading the data from the firmware and OS images prior to them being activated for booting into them, so it could read the data but now it appears that it can't. You should boot the device into recovery and sideload an equal or greater version as an update package. It sounds more like you have corruption of data rather than the OS, unfortunately, so sideloading probably won't work but is worth a try.
Moderator note: This comment was edited to include citation. See https://discuss.grapheneos.org/d/20415-grapheneos-version-2025022800-released/13