Latching relay is fairly new component in my parts bin and I was exited to use them in new circuits. Using microcontroller to switch off it's own power using latching relay may sound silly, but it's actually a decent way to implement this safety feature. Many laptops have features similar to this "storage mode": A small switch somewhere near the battery, pressing it disconnects the battery until the charger is connected... Made especially for disconnecting the power before taking the laptop apart.
sacrificing a latching relay and an entire micro controller for a functionality that trivial is pretty wasteful , especially when there is already a tp4056 circuits that have the exact type of protection you want built in.
