At my residency one of the side effects of the increasing midlevel presence was that weekends and holidays have been disappearing for residents. Apparently most midlevels charge extra to work those days, so it was cheaper to force the residents to be 100% present on those days to keep the hospital adequately staffed. My second year they told us Interns, who used to get one major holiday a year, would now get none, and they're now talking about extending that policy to senior residents. Also about half of my services had switched from a policy of one weekend day off per week to one random weekday. These policies are obviously a great way to make sure that residents are completely isolated from both their friends and family, since you wouldn't share a day off with anyone you cared about for months at a time.
I think the birthday idea is a good way to give residents at least one day off that has some meaning for them, in a training system that is showing ever less respect for their time and mental health. It emphasizes the idea that your birthday is an event, and should probably end with at least some kind of celebration (dinner with friends). Otherwise it becomes just another workday like Christmas, New years, and Thanksgiving.