From what I’ve read, Disabling AMT through BIOS simply passes a request to the on-CPU ME coprocessor to disable the functions.
That state flag is then stored on-CPU in a small non-volatile (flash/sram?) area for settings and other power-cycle maintained values/state.
There is no published external command or other signal to tell the ME to enable the functions again and Intel claims they have not implemented such a command.
B