Similar situations as with projector rail happen with rail_turn variants (they rotate), lock rails (they toggle), and signal switch rails (they cycle through states).

IMO Although for others it seems intuitive (like for chest - RMB is opening, Shift+RMB is placing block), I don't see any right-click behavior for projector rail, so that case should be fixed.

This is intentional. Right clicking a projector rail re-projects the breakable portion, allowing you to easily reset it to full length.