First, one must identify which deparment or army they are writing of and when were they raised. Dunlap's book, Lee's Sharp Shooters or Forefront of Battle, applies only to the ad-hoc battalions raised late in the war within Army of Northern Virginia and not all sharpshooter battalions in the Army of Northern Virginia were raised on the standards mentioned by Dunlap.
In other theatres, entire companies were transferred regardless of the ability of the men. Thus the origins of the First North Carolina Sharp Shooters that served in the Army of Northern Virginia. This practice was more common in other theatres. Understand that sharpshooting to most infantrymen and officers, was just another onerous task that needed to be performed. Thus, it is not unusual to find draftees who were were inducted regardless of their woodcraft, bravery or marksmanship ability. One substitute petitioned for his discharge on the basis of stomach ailments, arthritis and failing eyesight. Considering he was at least 61 years old (he claimed 71 in his petition for discharge) and more suited as a hospital attendant, he would not be anyone's first choice for sharpshooting duties.
The above is fully discussed and supported by endnotes in my article, Confederate Sharpshooter Selection, that appeared in the Summer 2009 issue of The Military Collector and Historian. Administrator Dave Sullivan (DSulli7875@aol.com) can sell you that issue of the magazine. Better yet, gwine (join up) and list me as your sponsor. Dave has another article that awaits release and it has material not contained in my book on the blackpowder sharpshooter.