Due to the weight of the frizzen bouncing, plus the weight of the cock and flint snapping forward to stop on the lock plate after scraping and bouncing the frizzen forward against its feather spring in comparison to the weight of a caplock's hammer snapping down in a cap, stopping there, the flint ignition has less potential for precision accuracy than the caplock.
I present that statement as actual fact (unproved) on the assumption of more jarring movement of the gun prior to the gun's ignition with flintlock ignition, than in a caplock gun. This does not even take into consideration the slower ignition of the flintlock wherein even more movement would be probable.
Excess gun movement is why we didn't use the available Wolf 30 pound main springs in our Mauser Actioned 3 position match rifles, and stayed with 24 pound springs instead. The lighter springs were more accurate due to less jarring movement prior to ignition. It is common knowledge that the faster the ignition, the greater the accuracy potential the gun has. This is why match and benchrest actions are built to limit "lock time" and jarring. In them, lighter firing pins, with sharp acting, short springs are used. The same idea goes for muzzleloader movement, only on a grander scale. Note the distance the hammer falls on most ML full bore bench rifles ie: short for faster ignition and flame straight into the powder charge, no bends.
With the modern stuff, I was referring to less than 1/4" grouping difference at 100 yards, whereas with the ML's ignition time differences, the accuracy difference "should" be even more pronounced.
This may not be fact, but logic says it is.
Note the double bounce of the frizzen EVEN BEFORE the pan ignited in the flint videos. That bouncing must move the gun, not to mention the shooter's inability to hold perfectly steady. Shooting off the bench will probably limit the gun's accuracy to actual movement during ignition, from the causes mentioned. I've been fairly consistently capable of shooting 1/2" groups with both my .40 and .45 cal. flint guns, however, doing that with the .58 double (single barrel groups as both barrels opens the group to 1 1/8" slightly vertical group) or my .69 is a whole lot easier. They are both caplocks. Not proof by any means, but still corroborative evidence.