I wonder if the 5th's are more prone to wind shear as are the semi trailers?
I'm not sure what Jim means by "wind shear" here - probably not the correct
meteorological meaning - but I'll guess the concern is being affected by crosswinds.
Does that height raise the center of gravity of the 5th vs a 21' bumper pull??
Not really - the massive objects are all the same height they would be a 21'. The "tongue" section of the frame is higher, and the body around the bed (which is basically just empty shell is higher, but those are not a big part of the trailer. The height of the centre of mass (gravity) is probably not a lot higher, although it would be interesting to see measurements of both.
I think the biggest effect of the hitching height is the
raised roofline to accommodate a useful sleeping loft and join the part to the rest of the trailer - this does raise the height of the "barn door" facing a crosswind. Fortunately, the increased side area is forward of the trailer axles, so a crosswind will tend to push the rear of the truck out of the wind, steering the truck into the wind, which is the right direction for stability. Also, as with any hitch force, that sideways push is more easily handled by the truck when it is forward near the axle, instead of back at the bumper.
The downside is that
hitch forces are up at hitch height, instead of less than half that height with a conventional "bumper pull". This doesn't matter in the big rigs, because their fifth-wheel hitches do not pivot side-to-side like modern RV hitches: the truck and trailer are rigidly linked in the roll axis, so the height of the coupling doesn't matter.
A big difference between typical commercial semi-trailers and an RV trailer such as the Escape 5.0 is that for practicality of loading common commercial trailers have a flat floor completely
above the tires and hitch, so the whole load is quite high (with a huge unused space underneath). The RV layout has the main floor much lower, so it doesn't face nearly the stability challenge of the high semi-trailers.