Sibelius Music Boogie Mistery pattern

I know that this not about Pianoteq, and this topic can be deleted after some days, but I would like that someone could explain me how the Sibelius Music player web device could interpret the left hand a little different than what is right in the digital music sheet.
    The rhythm it's different, from what we heard from what is writing from the left hand pattern.

Take a look yourselves:

http://www.sibeliusmusic.com/cgi-bin/sh...reid=72828

Slow dow a little the "speed slider" to heard bether. The begining of music, the first lines.

Well, who can explain this mistery ???   :-)