I think this is a classic case of "If it aint broke, don't fix it!".

IMO, the SWB design is great as is. Why is this one done differently ?

Is it REALLY that it's expected to be seen as an improvement ? Or maybe just a change that was made in order to deflect any possible accusations of cloning the SWB/BVM tank, with some marketing spiel added after the fact to pass the change off as something that we have just gotta have ??

Gordon