If someone tried to save a couple dollars building a car and made one that you had to open the hood and disconnect the battery every time you were going to leave it parked overnight in order to prevent it from catching fire, that would be a car that's unsafe, the sale of which would never be allowed. If something has to be plugged in for hours, it needs to be safe to leave it plugged in for hours. Regardless of exactly when it stops charging. It's not that hard for manufacturers to build a battery and/or charging system that will shut off when it needs to so that it is safe.

The definition of safe for the general public for a given product may take a sentence or a book, but that's up to manufacturers and/or regulators to figure out and adjust for real world conditions. Clearly that's not happening.