Freehub movement on Reynolds hub--is this OK? The freehub on my Reynolds wheel moves a bit horizontally when off the bike. Is there a problem with it, or is it working as designed?

I think what's going on in that video is either a slip fit endcap has partially slid off, or a threaded one is loose. If they're slip fit than of course it will all be fine once the wheel is back on the bike. If threaded, they should be re-tightened.