the info you have heard is right.
When they first brought out CGM for Weed supression it was said to use 25lbs/1000 ft.
60% protien content is required in the CGM. Not a higher Nitrogen value.
The effectivness of CGM as a supressant is based on amount applied
10lbs/1000 = fert
25lbs/1000 = supression capabilities
The one thing with all the new ECO or Enviro products is that the amount of AI (Active ingredient) needed to work is getting higher and higher.
From an environmental point of view these products are not reducing impacts but increasing them.
If you want to use CGM as weed supression you will need to buy a forklift and many rat traps. No joke.
Does CGM work consistently and effectively as weed supressant?
I say NO.
CGM is made from Genetically Modified Crops.