Only slightly higher, though.
Generally speaking, aside from stupidity, bravado, and booze, the most dangerous thing to motorcycles is other vehicles. I have seen it repeated in various places that it is better for a motorcycle to only have threats come from a single direction, and from a direction they can easily see - namely, in front of them. If a motorcycle is going the speed limit, they will be passed regularly by people who want to go faster than the speed limit.
If, however, they have a slightly higher speed limit, this will significantly cut down on the number of people passing them, and nearly all threats (other cars) will be coming from one direction.
Motorcycles being allowed to use HOV lanes already helps significantly; people can pass motorcycles, but by-and-large people don't tend to merge in and out of the HOV lane as often, so a motorcycle isn't as likely to get side-swiped by a car merging into their lane.
I personally am not sure I agree with the idea, but it would fit what I have been told numerous times: It's best for a motorcycle to go slightly faster than the flow of traffic.