Pre cut patches "seem" to have been the norm in the 18th c., from evidence of grease and sometimes patches found in old patch boxes, and the lack of documented "patch knives". Also extreme wear on the dove tails of original wooden box lids indicating a lot of use. More so than if only used as a tool carry. During the big fight at Boonesboro, it was reported that the women spent time in a cabin cutting patches for the men, which were probably square patches. Cutting at the muzzle might have been done when time and circumstance allowed, but would have been cut with ones belt knife, and not a special knife carried for patch cutting. Then we can move on to coned muzzles, which some, or many, believe most, or many were. If a muzzle is coned enough, or the ball size is small enough that a patched ball is easily thumbed in, what holds it place as you cut? Another point to ponder is wasted patch material. In cutting at the muzzle, you have to waste enough to provide a grip on the cloth so as to not cut yourself, and the waste is considerable when you add it up shot for shot. Pre cut square patches leave little to no waste, when waste might be a concern. There is no measurable difference in accuracy between muzzle cut, square cut, or round cut. As long as the patch surrounds the bullets waist, it will be as accurate with any of those.