Triple buffering does nothing unless you have vsync enabled. vsync links your card to the frequency of your monitor. e.g. 60hz . If vsync is enabled then triple buffering might get you a higher frame rate than your current refresh rate.
Graphic card performance is related to many different aspects of your machine- mobo, bios,hd access speed, codecs,64 or 32 bit os, ram, monitor(s) etc. None of which are mentioned regarding your test machine.
To test this on one machine and say it will work for everyone is not correct. To state it should be in the manual.....
If I am incorrect-you can slap me with a trout.