Grays, in my personal experience, are one of the hardest species to switch to a good diet. A gray I had took 5 years to eat a diet rounded enough to please me so don't give up. But what you need to do is cook whole grains lightly (the outside soft but the inside hard) and mix a tiny bit of small seeds into them (millet works), put the mix in the bowl and just leave it there all day long. At night, take this bowl out and give them 1/4 cup of seeds for dinner. Once they go to sleep, take the bowl out and, in the morning, give them the cooked grains with the seeds again and keep on doing this until they eat the grains (you will find empty grain 'skins'). Once they eat the grains, you can start gradually adding cooked vegetables.
I would not use a parrot diet reference so old. No studies were done before that, the first one was the Roudybush and UCDavis at the Psittacine Research Project in the early 80's, and even those studies were terribly deficient in methodology (they fed them for a determined period of time and then kill the entire batch to look at their internal organs).
Link on the tiel one:http://www.roudybush.com/index.cfm?fuseaction=birdBrain.articlesRead&article_id=2
these are just the recaps that you find for free on the net, you need to subscribe to a scientific site (I belong to three different ones) to get the full studies
protein requirements in amazons: http://www.jagran.nl/PrimoSite/show.do? ... 648,354377
the best about macaw chicks because it was done in the scarlet preserve: http://www.jagran.nl/PrimoSite/show.do? ... 648,504965
protein requirements of three different species: http://www.jagran.nl/PrimoSite/show.do? ... 648,246732
about grays and digestibility: http://www.jagran.nl/PrimoSite/show.do? ... 648,211060