It doesn't work, because RPi needs too much wattage.
I thought so too, but it seems some tv's can deliver enough power. In the first post it is confirmed: "I can run the Pi off the TV USB port, but only by itself as the TV’s USB port does not have enough amps to drive both devices at once" it sounded like he talked about the RPI4B, so i am curious if it works for more people before upgrading my RPI3B to RPI4B