Thanks for pointing and I know it. But the body would need that small amounts of glycose first. For example the brain won't be using ketones only. It will still use some glyocse but mostly it goes over to use ketones. Glycogenesis will support the glycose for that need and if the brain uses the glycose there would be hardly any glycose left for the cancer cells ? (I am not sure about this but I have read that the body needs it's glycose needs first and the glycose that is left over is bad)
There is an alternative treatment for cancer in which they induce a controlled insulin coma. The idea is that the cancer cells, which have a higher metabolic rate will starve faster than healthy cells. But still all the cells need glucose, not just the brain.
And the lack of fiber in the diet will still starve the flora, which among its many functions makes up about 80% of the immune system helping to prevent a number of diseases. This is another example of why I am against any strict diet such as all meat, all carbohydrate, vegetarian, all raw, etc.