Escape has always taken you back to the menu in GRUB. If you want to boot with your changes, press F10 or Ctrl-X as it says at the bottom of the editing screen.
Using TAB to change options is more an isolinux thing, but we don't use isolinux for the DVD any more. That means we can keeps the ISO images unchanged on the DVD for those that want the separate images files, but it means you lose some of the features of the distro boot menus as we have to bypass them, although we do reproduce all the options.
"Insanity: doing the same thing over and over again and expecting different results." (Albert Einstein)