[jlg23]

> Every feature has a cost. Not just cost to develop, but cost to maintain.

A generic implementation that handles any orientation could just be the implementation with lower development and maintenance costs?

> surely it’s clear why not supporting arbitrary display orientations is at the very least an extremely rational choice from an engineering perspective.

That depends on the engineer. For some it might be easier to consider the special cases (landscape and portrait) first while others don't even want to be bothered with them until optimization time because a generic solution is the more straight forward approach.