The point isn’t improved range — at least not in the general case. It’s just another driving option you should pick (or not) based on personal preference. About the only time it’s likely going to be good for regen is in stop-and-go traffic.
Personally these days I almost always drive within the city using 1 pedal driving — it’s super convenient, and starts slowing faster than a human can physically react to move from the accelerator to the brake pedal. If you’re using it correctly it will help your brake pads stay good for a crazy long amount of time.
But if you’re looking for regen optimization, 1-pedal is only the best in certain circumstances. Indeed, there really isn’t any “best” for all situations (although cars with dynamic “Auto” regen come close — or at least closer than a human likely can). Some say you should keep regen off altogether and coast — but that’s not a good option if you’re highway driving from a higher elevation area to a lower elevation area (as happens in mountainous areas). I spent part of last week doing a road trip through mountains towards the coast — overall the drop in elevation was around 600m (over several hundred km’s), and driving in Level 0 regen would have required me to ride the brakes throughout much of the trip to keep from accelerating too much on the steeper stretches. I was able to watch the battery percentage go up on certain long downhill stretches without loss of speed thanks to the appropriate regen level.
Point being, use what is best for your driving style and conditions. There is no one “best” setting — and 1-Pedal is likely only best in a certain narrow set of circumstances. Use it because it fits your driving style, not to maximize battery life.
The IONIQ 5 handles are still mechanical, and aren’t any more likely to malfunction than any other mechanical door handle. While they’re recessed, they’re effectively like a see-saw, in that you push down on one end to pop out the handle on the other end (a purely mechanical operation — it’s just hinged in the middle with a small spring). When you pull on the handle, it’s still just a mechanical operation to unlock and open the door. Now there is a motor that can auto pull that handle in and out — but even if the car battery is dead as a door nail popping it out by pushing on one side and pulling out the other is quick, easy, and works 100% of the time as it’s purely mechanical.
So there is no hazard — or at least, not any more than any other mechanical door pull.
You can see a video of the process here. The video is more based on how to open the door when the keyfob battery is dead, but it also applies if the car itself is dead.