I have to say, I haven't seen the RCMP use the term “combative”. I think that might be a colloquial term. The term the police services have agreed to use is the term “assaultive”.
A person who threatens assault may not actually be physically carrying out an assault, but they've adopted a posture or they've somehow signalled an intent to assault. That would constitute a threat, and that may very well justify the use of force—in this case, the use of a taser. That's different from somebody who's just standing there and not following orders.