Jonathan, as usual, raises a good point, pushed further by Bill.
Both seem to start with the conclusion that whatever Vernon did was probably perfect, and if we criticise it, then it just means we don't understand it.
Now, frankly, that is, generally, my view!
But here - a) to me the fingertip count looks no more fair than (say) the count in Card Finesse 2. and b) it does not look natural - and yet Vernon was always emphasising naturalness.
As Hallas mentions, Elmsley hypothesised that Vernon knew of the Avis handling, and used that.
And yet, as Jonathan points out, it is very unlike Vernon to accept a move without thinking it through.
So - that puzzles me (as does his Gemini Card trick...I've never understood the justification for putting the cards into an envelope - but that is another story)
But - I'm quite happy to accept that this simply represents, once again, that Vernon was lightyears ahead of me!
Also it is worth emphasising that the "twisting" action leads perfectly into the count; and those who readjust the cards after the twist are missing the point.