Chevy & GMC Vans

I once found a YouTube video that described starting an Astro van. You put the key in the ignition. Then you turn the key to the run position. Then turn the key back to accessory position. Then remove the key and you can start the Astro van without the key.
I can do this on my 2004 Astro van. Anyone know this video?

You probably need to replace the key cylinder and ignition switch. But I don't understand how the Passlock immobilizer doesn't kick in unless you've defeated it somehow.