Although i do not agree with the way they state things are connected, they are not wrong.
I feel it is better explained like this.
There is the physical body and the emotional body.
Both of them have organs in the same place that do about the same things.
Like our stomach digests foods and emotions.
Cancer starts on the emotional layer, and as you stuff more and more emotions into the area, it basically becomes like a black hole, and then it starts to build into the physical body causing a tumor.
No cancer healing has occured without the patient fixing the emotional stuffing problem first. The doctor can remove the tumor through surgery, but it is still there and will return, has returned.
Fortunately, you can heal the problem on the emotional layer and the cancer on the physical layer will disappear.
I think there is an even more integrated model that is involved here than what GNM has identified, however, what they have identified has been rigorously tested and outlined by Hamer and his GNM colleagues. I do however see some important extensions to the GNM model that go in the direction of what you indicate. Memories (mental or emotional) are not held in the brain but rather within the tissues and organs themselves. (This is why people that receive transplant organs also gain memories and character traits from their donors - here are a few examples.)
The brain is more an indexing organ rather than a storage organ. This has some significant ramifications on the GNM model. It means that physiological damage to the tissues, organs, and meridian circuits will make you far more vulnerable to conflict shocks and dis-ease. It also means that the Chinese medical model is correct in its correlation of organs and meridians to specific emotions and conflicts. This is a further extension and alignment of the GNM model to ancient Eastern medical models that should be addressed by GNM.
And, our current "medical" doctors only begrudgingly think that emotions have anything to do with the body. When you talk to them about a direct connection, they will throw you out.
So, i am glad for GNM and other such things. See "Hands of Light" by Barbara Brennan for an even earlier example. It is high time we start working holistically with the body.