I always scroll down to the bottom to check which actors birthday is today but there is something I always notice. It never shows popular actors like today is Kazuya Kamenashi's birthday but he is not listed down there. At times it just shows random actors birthdays instead of showing some more popular ones. 

I think it is chosen from the first few alphebetically. I thought there was a way to see a full list, but I can't seem to find it.

It is indeed in alphabetical order, and if I'm not mistaken, there are at most 12 people on the front page. So yeah, lots of actors/actresses,  even if more "popular", cannot be seen.
I didn't know there was a way to watch the whole list, I don't see where it could be...