Something to remember.
On the 787 (also 777 and 747-8), when the fuel control switch is cycled to CUTOFF, the electrical generation doesn't stop when the engine N2/N3 drops too low - it happens much sooner than that.
In order to facilitate a 'breakless' power transfer during an engine shutdown, the fuel control switch sends a signal to the electrical system, which reconfigures to drop the related generators from the system before they drop off line. This takes ~0.25 seconds, not the several seconds it takes for the N2/N3 to drop sub-idle.
So in the case of the Air India 787, the system would have lost all main-bus power generation a fraction of a second after the second fuel control switch was moved to CUTOFF, commanding the RAT deployment.