Doubt on Rechargable LED Emergency bulb
The Youtube video analysis is quite complete: The bulb tries to pass a tiny DC current (battery voltage through two 1 M&Omega; resistors) through the line connections, on the assumption that there is SOME DC path through the network at all times (even if it's through the pole transformer).

The light comes on if it receives full voltage from the line; this is "normal operation".

The light also comes on if there is no line voltage, but there's a DC path between its two contacts; this is "emergency operation".

Note the restrictions: The special bulb must be the ONLY bulb on the switched circuit. If there were other regular bulbs, they would provide the DC path and the special bulb would stay on all the time.

The demo video is actually using two outlet strips. One is plugged into the wall, and the black lamp is plugged into it, along with the second (switched) outlet strip that we see sitting on the table.

When he unplugs the first outlet strip from the wall to simulate the power failure, it is the black lamp that provides the DC path that allows the special bulb to switch on and off. Without that black lamp, the demo would have failed! (Also, if the presenter had switched off the black lamp during the simulated outage, the smart bulb would have switched off, too.)