All these footstraps look a lot like just that, footstraps. I tought the idea was to use them as toestraps, just as on windsurfers. I for sure would not want to do a pitchpole with my foot/ankle firmly in one of those. Isn't this how Glenn Ashby broke his ankle some weeks ago?
It is possible but i usually only have my toes in there max - just enough to hook onto. GA over balanced when looking backwards and fell between the hulls when they were sailing back to shore and did manage to get his foot stuck in the strap. General advise is to keep the strap relatively loose so that you can hold it taught in the forward position but so it is still loose enough so your foot automatically slides out when things go really pear shaped.
Tiger Mike