By rereading your description of your issue, there's something else which looks odd to me. You wrote:
But this normally cannot happen: whenever any object is right-clicked, the pie menu appears centered on the mouse cursor
(i.e. the mouse cursor can't be over a pie slice on pie pop-up), and when not possible (i.e. the object is too close to one of the viewer window borders to allow displaying the full pie menu centered on the pointer), then the pie menu appears in a slightly shifted position (so that it fits the window) and the mouse pointer is automatically and immediately moved to its center
, thus not letting it hover on one of the pie slices (since, indeed, releasing the right mouse button while over a slice is equivalent to left-clicking that slice: this is the normal and expected behaviour).
So the problem could be that, on Mac releases (because it doesn't happen under Linux or Windows), the mouse pointer is not properly repositioned at the center of the pie... Catten, could you please check that ?