Barrel harmonics plays an inportant role in accuracy, which has been one of the selling points of the BOSS system (you can adjust the barrel to the load and not have to work up the load for the barrel)...
It's all a function of when the bullet is exiting the barrel (at what point of the barrel whip does the bullet leave). Of course, this is mostly a function of velocity. Slower or faster means that the bullet is leaving the barrel at a different point in it's whip...
This being the case, any slight difference in burn rate, lot to lot, will affect accuracy. If you've already worked up a load for maximum accuracy and you then alter the velocity, the accuracy will 'suffer' slightly...
Of course, the temperature that you shoot the same ammo in will affect the bullet velocity and, hence, accuracy of the same load fired at different temperatures...
My point, of course, is simply that the quick answer to your original question about accuracy effects is, "Yes"...
But, since the temperature that you're firing the ammunition at will have a similar effect, the effect on accuracy due to lot to lot variation is somewhat unimportant.
However, since some powders display quite dramatic lot to lot variation, other aspects of the lot to lot variation are important to keep in mind. Like, for example, potentially blowing your gun up if you're loading to the very top edge of pressure to begin with...
Forrest