No, not "unfair". Disappointing, perhaps. The Dining Plan is arguably underpriced -- just look how popular it is, and how happy so many guests are with it. I would make sense to bring the value and the price more in line with each other, either by increasing the price (not my preference) or modifying what is offered.
Some DIS members have pointed out that there actually is an inequity going on, but it is with regard to non-Dining Plan guests, who have to "suffer" through circumstances that are arguably the "fault" of the Dining Plan. Rules that apply only to the Dining Plan would address those problems.
Desserts seems like a likely approach, and maybe appetizers too, but not-so-much with regard to entrees. One of the selling points of the Dining Plan is how much like a regular restaurant experience it is -- that exclusions and limitations, while assuredly evident, aren't onerous or prevalent.