Goes back about 15 years or so, say the theory was that if all ledgers ran left to right inside and out as the scaffold swayed the joints being in the same direction could both undo.
thus if inside runs left to right and the outside right to left one joint is always tightening. Theory sounds logical.
I did include it in a soft back edition of an operatives guide I compiled at the time.
Ken Johnson was the font of all knowledge on Tube Lock at that time, now it would be Steve Whatley must ask him next time I see him.