While in ortographic view mode (top, front, etc.) in editor viewport, Game view toggle (default hotkey G) cannot be toggled neither from the menu (where it is greyed out, see attachment) nor via hotkey. Note that view mode is set to lit.
If however I switch to perspective, I can toggle Game view, and then when I switch back to ortographic it remains in that state, but is again untoggleable. In essence, I have to press three hotkeys instead of one to achieve what I want.