At 150+ I have noticed the sidebags *lighten up* the handling. Going straight down the road is no problem. But I have initiated a slight weave on my own on purpose by gently nudging the handlebars that doesn't occur when running the same speed w/o the bags. It's not a big deal as it goes away on it's own, but it's definitely a little different than w/o the bags. I am guessing the front end is getting a little lite, partially due to the aerodynamics of the bags, partly due to more weight on the rear (assuming bags are loaded). Let me repeat, it's not that big a difference. And at sub 130 speeds, I don't really notice anything at all.
I would say don't worry about it. It's lawyer-speak for covering their ***. I mean, they also say not to run a top box and the sidebags at the same time. WTF??