It's now a "matter of conscience"? Wow, things have changed since when I was a JW.
There really isn't any biblical admonition against birthdays; the JW's only instituted it as a rule to maintain crowd control in the Rutherford era. It's essentially an arbitrary, baseless regulation. And yes, it always mystified me that anniversaries and graduations were okay, but birthdays were not. Anniversaries and graduations, technically speaking, are artificial, manmade accomplishments and celebrations. Birthdays are pretty much unavoidable. Never got that.
I'm amazed that there is, as Truthseeker indicated in another post, a creeping movement of liberalism in the WTS. I hope it continues.