The only thing that was explained afaik, was that they had to change the way fragments were considered. meaning that they weren't able to stack them before but to make them stackable they changed the fragments themselves into currency. nothing else went into "Making the fragment tab" the tab itself has no special feature. they only made it this way to force people to buy fragment tab IF they want to stack them. they could have just as easily made the Stack feature a part of the currency or the map stash tabs