I think the "inbetweener" you are referring to is the pochette OM (old model). The link you posted referred to the pouch as "mini pochette". That actually looks more like the Pochette OM after taking a closer look.
The pochette OM will definitely hold an iPhone 6+/6S+ as I own one.
The inbetweener came with a certain bag, can't remember what bag.. It has been said in this thread earlier also.. But it is not the old model, it is totally different thing. This inbetweener is 4cm (approx 1,5inch) smaller than the old model and 3cm bigger than the minipochette.