"Militia", what that meant then.

[Minimalist]

There actually was a reason behind this kind of training and various nations used different variants.



Volley fire, by rank, made sure that 1/3 of the battalion was firing, 1/3 was ready to fire, and 1/3 was reloading at any given time.  And it wasn't particularly suicidal to march up at 100 yards as with those muskets at 100 yards you may as well have been on the moon as far as effective small arms fire was concerned.  They would break out of march column and into lines in order to lessen the impact of artillery fire.  A cannon ball going through a column could take out 20 men.  The same ball hitting a line would take out 3.
The thing is you can't train individual militia companies to act as a battalion in action because you can't get them all in the same place at the same time especially in the colonies where the rural population was too spread out.  

This is why Von Steuben's work at Valley Forge was so valuable.  He taught them proper drill.  The British were properly surprised at Monmouth as they retreated from Philadelphia to New York.