It is a way to get your fly and line off the water and still load the rod on a roll cast. But the real reason to learn casts such as this is it develops your casting and feel for the line in circumstances when casting is awkward.
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I dunno. Maybe I am missing something, but to me, it just looks like a roll cast with a double haul. I don't see the advantage over a roll cast. But hey, whatever works for you, stick with it.