Yes, that's official. I am inclined to agree, as I think it contributed to at least one serious accident last year. I love my Kevlars, so much more comfortable, and easier to move around in, but, no braking in the material, unlike leather, so you just slide till you hit something.
Maybe some material will be developed that can be "striped" in to add that stopping factor, but I can't see there being much effort put in, as sidecar passengers are not a very large or lucrative market.
I'll keep mine for the road, where they are great, cos they are so stretchy, and , in the meantime I'll try to figure out how my leathers have shrunk so much...