The threads are closer together and therefore there are more threads holding your boots down. this video explains it pretty well. http://vimeo.com/29835967
LF has been nice enough that they plan to include the bolts with the board and with the boots as well. everyone will have the necessary hardware provided them no matter how they mix and match brands and years of gear.
maybe there are imperial bolts that accomplish the same thing i don't know, but maybe it was easier to go metric since everything else is made outside the US
Oh, and LF is not the only ones that made this switch, check out LWA wakeboards http://lwa-wakeboards.com/
i kinda wish the imperial system would just die anyway. we, americans are pretty much the only ones using it on the planet. it would take time getting used to but OHHHH so worth it. soo much easier to calculate and remember and make sense of.