Keep in mind that this thread was started many years ago. Even when the OP wrote it, their experience was the exception rather than the rule. There have also been cutbacks since this was originally posted ( and the experiences of the OP go back over many years of birthdays).
At one point, relatively few people even knew about the pins. Five or six years ago, we could be in a park for a day and see only a handful of people with any kind of celebration pin. It was also rare to see a group with special celebration shirts like the OP made - we could be in the parks many days in a row without seeing any.
On recent trips, we could almost always see someone in line or where we were walking/waiting with a special pin. And the special celebration shirts are getting more common. We might not see a group every day, but close to.
With so many people celebrating, there is no way that WDW can give each person all the sorts of special things the OP mentioned.
So, go with the expectation that you will get a fair number of greetings, but anything else is pixie dust that most guests who are celebrating birthdays don't get.
Celebrate 
