Larry Jaques fired this volley in
news
The probable problem with that is that the ball would be creating a
bit of a venturi effect, vaporizing the liquid before it could get
through. My best SWAG.

Larry, you're correct, but we still had to "challenge" the concept.

It's the case that the common propane cylinders do NOT have a 'dip tube',
just a top-valve/oriface. In fact, it _appears_ that the ball-check
produces less of a pressure drop than does the 'micron filter' just
preceding the outlet, so there is a remote possibility that the tube
between valve and tank _might_ fill with liquid. I think it may have -
at least some - since the 'burp' I got when running it inverted was a bit
longer (by a fraction of a second) than the burp gotten when I burnt it
upright.

The whole thing is a scam, to confuse people.

Lloyd