http://www.dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/w/index.php?title=Dev/Leak_Tests&curid=264&oldid=83683
Source: personal experience of Whonix developer Patrick. There are probably many people on search engines confirming the same. Please edit if you know any better sources and/or structured research in this topic. Operating System Detection Operating System Detection tests can be unreliable.