That "carefully remove the speaker grill" is the chosen phraseology means that these are instructions meant for maintenance and service, not instructions meant for emergency egress. Furthermore, the latch release cable doesn't provide much leverage and access at all, given it's literally at floor level. It's also possible that the latch release cable requires a lot of force to pull (if you have to pull against springs or pull against frictional forces on contact surfaces of latches). These factors make me conclude that this system was never designed for emergency egress purposes.

However, these are not an inherent issue; it's certainly possible to store energy (compressed gas, auxiliary battery, springs, pyrotechnic charge) to provide a redundant opening system in case the main power supply is offline. Using stored energy to activate emergency safety apparatus (hi, airbags) is not a new thing in passenger vehicles. Hell, some cars have pyrotechnic cable-cutters that isolate all non-essential 12V/HV circuits with explosives milliseconds after a severe collision are detected (to avoid post-crash fire/heating and electronics damage).

To solve a eminently predictable post-crash problem with "take off a speaker grill that's on the floor (right next to a battery fire) and pull hard on a Bowden cable" is simply not acceptable and the state of the art in post-crash systems indicates that Tesla could have done much better.