Yes, Andrew, we meant the same; just the Sporasub has the other types that are not so widely used. All manufacturers always make experiments.
About the footpockets. The most of users even very experienced believe, that the full version has the better performance. But you practically never hear this opinion from the finswimming professionals, especially the racing ones, where the performance is most important. We believe basing on our 10-years experience in this business and some investigations that we've put the money in that it's just a result of good marketing and nothing more! The full footpockets has a plus against the wide(!) strap only in one case - if you step on a sea urchin. The advantage in diving in very cold water is negligible because the rubber is a good conductor of the heat and we use neo-socks anyway.
If you have a look on the professional racing equipment of ANY manufacturer (monofins for the finracing, lifequardfins for the lifesaving) you cannot see the full footpockets. Why?! If the performance of full footpockets were better then the profi equipment would have only full variant. For competitions even a half of sec is important. The answer is simple: the full version is not better in performance then wide-strap one (good point -never use thin-strapped fins). Moreover, it's a bit worse. In process of kicking when the in the very end a finswimmer uses foot-fingers for extra-kicking that gives some additional effort (that's why using an open-toe fins is a really bad idea), that’s not so important as a kicking by legs but it doesn't worth to underestimate the finger-kick. Well, if your hill is covered by rubber or some kind of plastic it makes an additional elastic tension in process of your finger-kicking and makes it worse. For now no so materials for the footpockets that are able to remove that effect.
The other reason of using open hill for profi it's a size. Can you change a size in our full pockets? I can bet nobody can. What if you feet are between-sized as for 60% of population? What if you one foot longer then other (it happens quite often)? In this case you have to by a bigger size and use the socks. In professional strapped fins you can just reglue the straps (never believe mechanical fixing of strap like buckles for serious finswimming!) it's fairly easy and you have exactly the size what you need that very important for swimming in fins for a long while.
The third reason is not so important, but in the fullpockets the load-bearing part of strap really thinner then in strapped fins, it's a question of production process and it's almost unreal to avoid.
The last reason practically is not so important.