Backfeeding houses with generators is indeed a killer feature... but not in the way you mean. It can be done safety, but when done incorrectly (if the house isn't removed from the grid first) it can kill linemen. It's a good thing most generators a homeowner might causally buy at the hardware store don't have this feature. Unfortunately I've seen male-to-male extension cords sold online for this purpose. I think these are actually illegal, at least in some places.
https://www.cdc.gov/disasters/elecgenerators.html