Iirc Ducati have used adjustable rake on both their race bikes and some of the road homologation "R" models, so it's not a new idea to vary the rake in that
way afaik. I can't see how it would vary the rake if the bars were turned, but you'd only have two options of rake from what I can see, anything other than adjusted fully forward or back would result in the steering head / forks being at an angle to the vertical axis of the frame - the forks would look p*ssed in other words.
Mind you, theres still the question of what happens when the internal bores of the bearings aren't aligned, perhaps they are spherically floating bearings - similar to a rose joint.
Oh and if you adjust both top and bottom bearings together fully forward or back you could adjust the steering offset. If you really wanted to of course..... My brain hurts now.
Pic nicked from Ducati.org btw.