Sorry Ray, I missed this somehow.
However, read my sentence again "There are some variations now that have a tube fitted so that, like the in-line closed end feeder, they can be fished in-line, but many anglers regard these as no more than a gimmick."
It's what I hear. No doubt there might be a very odd occasion when some sort of rig like you say just might catch a fish or two, but you have always got to ask yourself, is there another, maybe better, way of presenting it that's tried and tested.
My point being that you can take anything used in fishing, add a little something to it (in this case a tube) and says it's "revolutionary".
Over the years there have been lots of little twists on standard bits of equipment all claiming to have "the edge", but few stand the test of time, sadly.