Well Kim since celiacs can eat some grains, I don't know that mycotoxins would be the issue. If as you say mycotoxins are in all grains (I really don't know), then it would stand to reason any grains would be a problem.
However, celiacs can consume corn, rice, millet, teff, sorghum, buckwheat, quinoa, etc, so I don't know how much an issue mycotoxins would be.
But, for the general population (non-celiac), I would imagine cutting down on grains would be a benefit to your health.