How Often Is "Contributors" Section Updated on Bitcoin.Org
It seems that the list of contributors is automatically generated by this script:
https://github.com/bitcoin-dot-org/Bitcoin.org/blob/master/_plugins/contributors.rb
and is refreshed every 24h (as stated in a comment in the script itself).
I suppose that the difference in the counts depends on the fact that anonymous contributions are excluded in the github API request (you should add anon=1 to have all contributors).