Does human digestive system benefit from eating same kind of food consistently?
I think it would depend on the benefits you are looking for.

If you ate the same thing everyday, it's possible your intestinal flora, and the rest of your GI tract would optimize themselves for maximal nutritional extraction. It is known that the flora in you GI do affect nutrition. I recall reading about obese patients who had gut-bacteria which made more nutrients available.

However, if you were in an environment where your diet could change unexpectedly, this optimization could actually be detrimental, since you wouldn't be ready to switch foods when necessary.