I don't know a lineman who doesn't assume the wires are hot. They have more to worry about all the solar generation feeding into the lines than me. At least I am doing the switching manually instead of automatically.
I was planning on turning off the main breaker on the panel first. Either that or I can just pull it out. How can electricity go to the grid if you do that?
"If you do that" of course it won't. And if you, or someone else doesn't do that?
Sequence counts. If you disconnect from the grid before you connect to the generator, there's no way to get it wrong.
But it's possible that someone else who doesn't have such an awareness could be using your equipment. It's possible that you could get complacent and have both on at the same time. Is it possible that it's 0300 and you're sleepy and it's storming and the power is out, and you screw it up? Maybe and maybe not...
I try not to be an idiot, but let me tell you something stupid I did while tired and rushed : I was unhooking my pickup truck from a gooseneck trailer. I dropped the tailgate, released the chains, disconnected the cable, opened the latch, jacked to clear the ball, slammed the tailgate shut, jumped back in the truck, **and pulled forward destroying the tailgate with the gooseneck**.
Obviously I knew not to close the tailgate. That didn't stop it from happening.
Why not use equipment that physically won't allow generator and grid connection at the same time?