No it would be a fact if they contain toxins.
Just because a snake is only slightly venomous it means it's not venous or it still is??
So you are now agreeing that grains contain certain toxins?? So look who is back paddling, I can now feel that truck reversing over me. No one including myself ever suggested what the level of the being poisonous is, but the fact remains.
It's poisonous enough to kill stock if it's not accustomed to eating grains, so yes if it contains toxins it is poisous.
Just like apples seeds, cucumber skin, raw potatoes etc etc are poisonous, does not mean you take a bite and keel over and die, but never the less they are poisonous.