Yeah, the synthetics are more concentrated, but will deliver less iron (lbs/1k sq feet) than milo.
Milo is just an organic vs a synthetic. You put down a lot more product with Milo compared to Scotts.
Milo is recommended to put down 32lbs per 2,500 sq feet or 12.8lbs per 1k. Out of that 12.8lbs 2.5% is Iron. Meaning you are putting down 0.32 lbs of iron per 1k square feet.
Scotts green max is 16.67 lbs per 5k sq feet or 3.33 lbs per 1k sq feet. Scotts is 5.17% iron. Meaning you are putting down 0.17 lbs of iron per 1k square feet.
Pennington is 14lbs per 5k sq feet or 2.8lbs per 1k sq feet. 5% of the bag is iron. Meaning you are putting down 0.14 lbs of iron per 1k square feet.
So, Milo is almost 2 times as much iron put down.