RE: Mathews Legacy fixed roller guard
I have a Icon and the limbs do travel a bit during the draw but honestly not that much. The Icon has a certain amount of preloading as well but the limbs are not as horizontal as the Legacy.
I think both bows gain a bit of performance from the roller guide as well. It reduces friction which is a great way to increase performance. What they are doing in a sense is "precocking" the limbs therefore reducing overall perception of travel. even on a bow with less of a vertical limb design you still get the preload which in this case reduces limb travel on the draw & release.