Understood.I did a post with some pictures a while back using a VDH flat plate and it works as well with my Freedom Plate.
The main advantage is bulk, the backplate has straps why pack it into another bag with straps. The dry bag is a 10 l that I bought in Thailand but you can find them on Amazon. I find airlines ignore anything you wear as far as reasonable bulk goes with the exception of some Asian carriers who weigh carry on stuff.
That last part seems to be why some people take the first stages off the hoses, not because things pack better in luggage or carry on, but because the first stages can go into pants or jacket pockets so as to not contribute to the weight of the carryon. I may end up having to test this this winter as I prefer all my essential gear with me (over arriving with essential gear in the luggage that is elsewhere) ... and carry on weight limits put quite a damper on how I usually pack...