Is this normal?

Get the height down.

 

Maybe it saves wear on the cylinders?

 

I would guess to guard against cylinder drift. I wouldn't think it would be a real issue, but if the manufacturer says "do this when in transit", then "this" should be done, whether or not it makes sense (please see "turbo dry spin").

Or boss man had a driver claim cylinder drift when the driver screwed up loading, so now there is POLICY.

 

It's when there's a leak inside the cylinder and it allows fluid to pass from once side to the other until pressure is equalized. From my (very limited) understanding it happens more at full extend and things drift down to "rest", and most often when the unit is being manipulated. My farmer friend has a problem with his sprayer booms drifting. To fix it he'd have to tear the whole thing apart, which would probably break more things than it would fix so he just deals with it until the 32% nitrogen rusts it out.

 

Cylinder drift is really only an issue if you are working against weight or gravity. The cylinders can leak internally and bypass and the cylinder can move. Buy again not against thr laws of physics.
Hydraulic oil does expand or contract slightly with temperature change but not enough to really move anything much. If the Hydraulic pump was running and you have a leaking control valve it could also make things move that shouldn't