I would offer that the primary reason there are so many 'more reported miss matched bolts' in Yankland is that all the Enfields, excepting some of the Savage-made ones, have been imported and passed through heaven only knows how many sets of hands in the process. I'd wager not all of them care a dot if the bolts matched the rifles, and that to most of them regarding Enfields, 'one rifle, one bolt, one magazine' was the rule of the day.
Admittedly, leaving any weapon cocked is not good practice, but after all we're not in the same room with it so ...