Looking at the website code, this was intended. There are several other hidden feeds however. I'll just sum them up below, so that you can make your pick.
http://sa-mp.nl/news-feed/updates.xml
http://sa-mp.nl/news-feed/updates-atom.xml
http://sa-mp.nl/news-feed/twitter.xml
http://sa-mp.nl/news-feed/twitter-atom.xml
http://sa-mp.nl/news-feed/news.xml
http://sa-mp.nl/news-feed/news-atom.xml
Note that twitter.xml is exactly the same as twitter-atom.xml.
http://sa-mp.nl/news-feed/updates.xml
http://sa-mp.nl/news-feed/updates-atom.xml
http://sa-mp.nl/news-feed/twitter.xml
http://sa-mp.nl/news-feed/twitter-atom.xml
http://sa-mp.nl/news-feed/news.xml
http://sa-mp.nl/news-feed/news-atom.xml
Note that twitter.xml is exactly the same as twitter-atom.xml.