I wonder how many people actually use these things in the way they were intended? To my knowledge, no one makes shoes anymore with the slot for the back edge of the pedal.
Way back when, before "clipless" pedals were invented, the drill was to do most of one's riding with the straps rather loose, but to reach down and pull them tight when one wished to sprint or climb a big hill. Then you'd loosen them up again so that your foot wouldn't go to sleep, and you wouldn't fall over like Artie Johnson at traffic lights.
Clipless solved so many problems....
We use toe-clip pedals on the police bikes, as we need to wear ordinary shoes for foot patrol or going into buildings. You'll not make many friends walking over a hardwood floor with SPD cleats digging divots... But no one uses them as described....We just use them as devices to keep your foot in place on the pedal. The "half clips" are very popular; thats the ones with the toe part only, and no straps.