Tim - you are correct. Squire recounted the story of the famous "Cove Spring Fight" right along present day US 127, near Harrodsburg, where this occurred. The "Cove Spring" is still shown on topo maps. The knife was referred to as being attached to his hunting pouch strap. I think the timeframe was around 1779 or 1780 give or take a couple years.
Couple of thoughts - I don't know how many documented pre-1790 pouches exist with the original strap in place , but if any, it is very few. I don't think we can draw much of a conclusion about what was commonly attached or not attached on pre-1783 pouch straps just by looking at the the surviving examples - there just aren't enough.
From personal preference, the only knife I use on a regular basis to cut patches at the muzzle is a slender House style knife with a relatively long blade - probably around 7 inch blade/11.5 inches overall - mounted to the back of a bag, and it works just fine - I just keep it really sharp. I have used pocket knives/folding knives as well, and just find it a lot easier to pull out a knife from a sheath mounted on the bag or strap - which all can be done with my right hand while holding the muzzle and the tightly gathered up patching material in my left hand, than to have to go into the bag for a fodling knife, open it etc. which usually involves two hands.
Of course, if you are cutting patches in advance from strips, any knife will do.
If you look at many surviving examples of 18th century American knives, many are smaller than what many of us think of as "rifleman's knives" today and would be equally handy as all purpose skinning, patch, or general utility knives.
One thing I have wondered about are the small late 18th century and early 19th century American daggers you see with one side of the blade with a medial ridge, the other ground flat. Maybe for cutting patches on the muzzle?
Guy