Does anyone else do the pinky count with their index finger along the side of the deck, instead of at the top, i.e. usual mechanics grip?

I learned it that way, and find that as a result I get a good grip of the deck between my thumb (on the left) and index finger (on the right). This allows me to have my middle finger and ring finger hanging loose, in a natural position between my index finger and pinky finger. The three fingers along the side look quite natural, rather than the odd looking ring finger which you tend to see in a lot of pinky counts. And perhaps most importantly, it makes riffling the pinky finger along the edge much easier - for me at least. I can count up to around 20 cards quite easily and consistently.

Is this a completely unorthodox way of doing the pinky count, or are there others who do it this way as well? And can you think of any good reasons why I should give up this method, and learn the more orthodox approach with the index finger at the top of the deck?

I think this is the way that Darwin Ortiz does it, with his index on the side.

It's probably because with the index on the side, the deck will be positioned higher on the hand so the little finger can riffle down the corner easier, where as when the index is at the front then the deck is positioned back a bit so the little finger has to reach more for the corner

Having experimented with it initially it is easier that way but I prefer it with my index finger in front as the changing of the finger position could be a tell you're doing a move. It's like someone going to deal cards and switching to erdnase grip, you know that bottom deal is coming. Not that this is something most spectators would notice..

I keep my index finger on the outer small end - but I'm not up to counting 20 yet. Perhaps I'll experiment with your grip a bit.

I notice my index doesn't really do much during the count, it stays pretty loose - unless I'm counting a face-up deck (then I have to curl it under the cards, otherwise they won't really move too easily).

I’m doing the pinkie count from a regular mechanic grip, with the thumb along the long left side of the deck, not on the upper left corner which is useless and less natural.

Good on you on finding this approach, one thing to keep in mind is that are you going to switch your index finger back to the outer end when you are not counting the card?
if you do, I suggest give up that method, because whenever you shift your index finger to the side compare to how you mostly grip the deck, audience might end up suspecting something is happening.

This is an excellent point, because it does have potential to arouse suspicion for this reason.