The way I've always perceived the "Granny Boot" was that it was a low-heel or kitten-heel ankle boot with a chunky heel and (most important) lace-up design. Or at least, that's how I've perceived Granny Boots from Newport News catalogs. Most of these are merely lace-up oxfords or lace-up booties.
Nothing to really get excited about with these booties, in my view.