The problem I see with using AJ in this way is that it starts out with a SG of ~1.050, and it’s not clear to me how this will affect the solubility of the additional sugars from the grain. Also, the grains absorb liquid from the mash, which if you’re using AJ (instead of water) means you are losing sugar to the grains, at the same time you are trying to get sugar out of them.
So when you conduct your experiment, be sure to measure volume in, volume out, SG in, SG out.
"Anything worth doing, is worth doing slowly." ~~ Mae West