This is absurdly paranoid with absolutely zero evidence. For embedded and mobile threat models where physical access or bootloader unlock is possible, eFuses are effectively mandatory for robust downgrade prevention

Agreed that robust downgrade prevention is necessary. However it's not paranoid at all and the problem isn't limited to eFuses. A network connected device that the vendor ultimately controls is a device that can be remotely disabled at the vendor's whim. It's like a hardware backdoor except it's out in the open and much more capable.