Why are ranged units mixing when moved together?

Before the warchiefs expansion, units moved grouped according to their unit type. Musketeers in front and skirmishers on the back. It made sence: Musketeers have shorter range and can deal with cavalry and skirmishers could use their superior range against enemy units while beefier musketeers soaked damage for them.

For some reason this was changed and ever since then ranged units are mixed at random in their formations. Never understood this change.

Whats the reasoning behind it? I know we just group our units according to their type but that change always felt like the dragoon pathfinding in Starcraft: something out of the player control that forces him to imput more micro.

Yes, this is why it’s hard to tell musketeers from light infantry.