Hello, Yggdrasil,

as i wrote, above,
when you turn your real cam, the roll (or captor) turns with the cam.
When you change ratio in 3D virtual cam,
virtual captor does -not- turn,
but changes it's vertical size.

Vue squeezes that into the viewer window at 72 dpi.
Moreover, the pix widths and heights, which programs propose for rendering,
do not result from ratio and focal length calculus,
they are "most used" formats.
So, if one jest pushes the button, it's not astonishing that results don't look logic.

Look at these renderings of the same scene :
nothing in the scene changed, same position, same focal,
but :
Left render Standard PC Vertical at -320- pix wide (427 high),
right render Standard PC Horizontal at -320- pix wide, too (240 high).
See what I mean ?

I hope this helps understanding.