Yes, Scotty's line in Balance of Terror about the Romulans using "simple impulse" has been a source of discussion for quite some time.
Of course, we could extrapolate, if the cloak was used but never revealed
as being used during the war, then Spock's line could hold some water- a cloaked ship can't fire a torpedo, but it could launch a "primitive space vessel" (an automated one) out the back of a cloaked ship. That primitive vessel would begin, at a set point, to suddenly start launching nuclear weapons at a planet. That would reconcile what was said in Balance of Terror, would it not?
The Romulans could wage an entire war and cause massive casualties without ever even risking one of their own ships, or a single crewman.