Do they open wide enough that the hooks could grip the battery posts from the inside? Keep in mind that (a) the posts used to be the highest thing on a battery, before the maintenance free batteries came along, which required more headroom for the cells, and (b) the posts are closer together on a six-volt battery, and, even on a vintage 12-volt battery, the posts are closer together than you often find on modern batteries. Cars didn't require quite as much battery back when radios and even heaters were optional!
Just had to replace the battery on one of our cars, and am grateful that they're building handles into modern batteries; I could not, for the life of me, find the battery-carrying strap, and the battery was in a box in the engine compartment, where it would have been a very devil to remove by gripping the sides.