Could be a combination of both. Looks like the narrow width of the pedal (where the straps thread through) is designed to be smaller than the base of your foot, this might leave more play in the bottom of the strap that threads through the holes causing it to sag when unsupported by your foot. Usually when you pair those types of velcro straps with wider BMX pedals the width of the pedal kind of supports the arch of the strap. Not sure if I am explaining it clearly, but I think it might just be the looseness of the bottom of the straps, and the narrow width of the pedal when the straps thread through.