"I was annoyed by the loss of fuel capacity, to get the tank full I had to compress the silly thing by hand so I could pull the nozzle out far enough to fill all the way and still have the pump run."
That's what the tool is designed to do. It holds the boot back for you so that you can actually top the tank off.
It just makes it easier.
I've used mine for about two years now and when we go on group rides my buddies always ask me where I got it and if they could have one. That's why I decided to start making them for sale.