[thebruce87m]

I would imagine the doors run off of the 12v system (or maybe 48v these days?) for safety reasons. The emergency release for the doors is for when that system fails.

The high voltage battery can actually sometimes be completely disconnected from the car during normal use, e.g. when parked and no sentry mode enabled.

[amluto]

The doors in older Model S versions had a single lever that would trigger the electronic window controls slightly before you pull hard enough to mechanically release the door. A complete electrical failure would not make it any harder to get the door open or even require additional thought, although it might be mildly impolite to the window seals and politely a bit more than mildly impolite if the door is closed hard before the electrical system wakes up.

I have no idea why Tesla changed this.

[penjelly]

yes, and it looks like this would be a scenario where the battery is totaled (unless fireworks?), which means doors are locked shut from inside and outside.