I suspect it is probably a tipping issue, based on some of the questions I've seen here over the years. A lot of people don't seem to know the general rule of thumb that you always tip on the undiscounted tab, and based on Disney's menu prices someone tipping based on some perceived notion of what a TS meal is worth on the plan rather than on the full menu price total would be a substantially lower tip for servers.
I don't think explaining the plan should be a problem; I don't think that's any different from explaining the specials or making recommendations. It is just part of the job.
I will say, though, that I've never encountered a server who seemed unhappy that we were on the dining plan. We used the basic plan a couple of times before the deluxe was introduced, and now we use the deluxe plan every trip. I do politely interrupt to let the server know that we've done the plan many times and don't need the full explanation, which might make a difference since it lets them know we're not going to be the family arguing over the plan's inclusions.