So, a person is out of step using a rare item, in this case a knife, for the purpose of cutting?
An Englishman living in upstate New York colony during the F&I kills an Indian and dispoiles him of his goods. So you suddenly have an English man with a Frenchknife and fusil. Not common for Englishmen, but he wouldn’t have thrown away a valuable prize.
A pirate takes a Spanish shipthen sells the booty in Charles Town or Baltimore. You think Good English men turned up their noses at Spanish goods?
That such a knife existed in nineteenth century and no special improbable story is needed to get in in to an American rifleshooters hands means he could have used it to cut stuff... including patches.