All you use gravel for is to "mark the trail", so to speak, and to hold the sand in place so it doesn't just wash away to the side.
Northern Indiana has more muck, and gravel stabilizes muck in dry weather to reduce dust. It does nothing in wet weather but if it's piled high enough it'll keep you out of the swamps.
Gravel roads don't work everywhere.
BTW, throughout the Midwest it is commonly the case that "gravel roads" are really pea gravel and tar concoctions that most folks can't tell from more formal paving techniques with heavier asphalt.
The city of Indianapolis has several thousand miles of peagravel and tar roads that are kept in shape by filling larger potholes with asphalt compounds.
So is that what they're talking about in Michigan? Here gravel roads are literally that: little rocks laying on top of dirt with no tar or other adhesive agent. Very dusty and little durability.
I don't think they're talking about the pea gravel. The article also talks about damage to windshields.