I certainly think it more likely that glyconutrients exert an immune stimulating effect by activating receptors along the gut wall than by acting as prebiotics. The prebiotic route sounds too convoluted IMHO.
We know for a fact that glycos are immune boosters. 80% of the immune system is located in the gut. Its doesn't take a huge leap of faith to put those two facts together and make the assertion that glycos act on the gut.
Its a very plausible hypothesis. I look forward to reading more.