I have long suspected that French Link and Dr Bristols get muddled up and mis-labeled in the saddleries.
My local saddlery store owner can’t see the difference between a KK (with it’s clever angling of the loops that hold the centre link/lozenge) and a regular SS version, whose loops are so placed that I reckon THEY dig into the tongue.
If the loops lie flat (ie on the same plane as the rings) then a plate will dig in - a Dr Bristol. But if the loops are turned 90 degrees, to allow the plate to lie flat, A French link, then the loops will dig in.
I only started paying attention to this when I put my nice old “French link” eggbutt snaffle on a young horse, and he would not, could not take a contact. He was unfazed by a KK, and even a single joined eggbutt or ring snaffle.