Don't know when it was added, but it was included on the sheet we got when we checked in last week. It doesn't help us, we only get there for breakfast, I enjoy their Tonga Toast and coffee!
We ate lunch at Tony's in MK last week a day before I read my check-in material. I'm still kicking myself over not realizing DVC members received a discount on lunch...Our bill(without tax and tip) was over $80!
Not sure exactly when it started, but we took advantage of the discount on our trip in May. We spent the day in MK and took the monorail to the Poly for dinner. With 5 adults 10% probably worked out to 12-15 dollars in savings. As an additional bonus the DVC discount did prompt us to try a new restaurant that none of us had been to before. We enjoyed it very much and would recommend it to anyone, especially as a nice break from the park before the evening parades/fireworks.