The layout of an array, landscape vs portrait was to install as many modules as possible in the available space, maximizing the size of the system. From your discussion regarding the bypass diode, I note that if there were any shading issues, orientation of the module, when positioned in landscape will have the least affect on the functionality of the bypass diode and thus module output.
That is correct for typical crystalline PV assuming the normal shadow pattern with the shadow coming from the lower part of the module as with inter-row shading as opposed to a shadow coming from the side. This way we will take one third of the module's production rather than all of it if the shadow was shading 1 row of cells.
Note: if the entire string is shaded with MPPT, then the PV source circuit would operate as if the entire string was in the shade, since shaded cells can operate at a substantial decrease in output.
Another note: with thin film PV, the cells are in stripes, so the PV will be oriented so that the stripes are north to south and the inter-row shadow will shade all of the cells the same and then shading is directly proportional to production (no series penalty if cells are all shaded the same).