Look into it more. It's incredibly common, and the voltage from a small generator in your yard, yes in theory, could leak to neighbors. However electricity follows the shortest path to ground. So if your home is drawing it, you will basically prevent that leakage. If you do fire it up, but use nothing, you may partially leak current to your neighbors (and potentially be liable for damages if your little backyard Honda or generac has a power spike at some point)

And the danger to to the linemen doing repair isn't the voltage necessarily (house current of 120v is not remotely high enough amperage to cause instant death. You can stick a fork in an outlet and try it) it is that you may suddenly electrify lines they are working on while suspended. If you charge the line, maybe you shock them and they have an accident. Or worse, your charged line creates enough of a charge differential that during the repair the much higher voltage electricity they have not isolated yet may bridge the air gap because you've energized the "dead" side prematurely.

In reality, most electricians and linemen are careful of this because of this exact reason. But it did harm a few people before moron's use of these things became common knowledge. Prior to these kinds of cables being commonly marketed for this, a lineman could hop up and reconnect you faster because there was an assumption they had full control of the current pathways. Now that's a toss up. This isn't a recent thing either, but it's becoming more common.