Well I’ve been driving over 50 years and I’ve not the faintest idea what the OP is talking about.
However I do know the “Correct” way to hold the reins:
for a single or pair:
In your left hand,
The nearside or left rein should be over the forefinger.
The offside, or right rein ordinarily between the 3rd and 4th fingers. I ordinarily put it in between the middle and 3rd finger but I’ve got big hands and decades of driving multiples!
Both reins should be held firmly into the palm of the hand by the lower 3 fingers. Or lower 2 fingers if you hold them like I do ordinarily.
For a team or tandem:
Nearside lead rein over the forefinger of the left hand.
The offside lead rein between the forefinger and middle finger.
The nearside wheel rein directly under the offside lead rein between the forefinger and middle finger.
The offside wheel rein between middle and third finger.
All reins held firmly into the palm of the hand by the fingers, the thumb resting lightly on the top of the rein.