no, it shouldn't be.
that's why we call it the Curly Holiday Swap and specifically say Hanukkah, Christmas, Yule and Kwanzaa are the holidays involved. if Diwali took place in December, i'd include it in the list.
the person who started this back in 1999 is a very devout christian and she didn't want it to be focused on one holiday. everyone should feel included, no matter what they do - or don't - celebrate.
and every person who has run this since then has done the same. including the devout atheist who's running it this year!