As far as I can tell from reading the Ordnance letters about the change to the buttstock, all they seemed to be concerned with was strengthening the wrist and not affecting what they called "The Exercise of the Musket", which we now call the Manual of Arms.
Marksmanship did not seem to worry them otherwise, the Cheek Recess in the buttstock would not have been done away with. Besides, they used Linear Tactics which relied on volume of fire, not accuracy. I don't think you could hit the broad side of a barn at 100 yards with these old smooth bores, or at least your aiming point.
It is telling though that when the design of the Model 1840 Flintlock Musket was developed, the buttstock of those muskets had a high comb to the butt and long wrist, as shown in the photo below.