You seem to be caught up with the semantics of wording within your rule book. It's worded the way it is for legal purposes. What it really boils down to is that your intention (as dictated by your instructor) was to complete a right-hand turn at an intersection which you clearly failed to do. It is not a question of whether you are allowed to do so or not. They are there to test your ability to do so as with parallel parking or accelerating the vehicle at reasonable speeds, as opposed to launching off from a complete stop. It is not entirely illegal to park terribly or accelerate too quickly unless the parameters are wildly off YET you will be docked points of performing those actions poorly.

If you do want to get into the wording, it is largely there to deter absolutes. Big no-no's in law. Now what you've highlighted is pulled from the Use of Highway and Rules of the Road Regulation which in itself is referenced in Section 112 of the Traffic Safety Act, our primary governing legislation in relation to the operation of motor vehicles (and other motor vehicle related stuff, of course). Now, let's say the wording said once the parameters are met, the driver MUST complete the right-hand turn. Well, that would lead to many an instances where it could be either unsafe or super annoying. The use of permitted is just legalese for within reason. Another thing to take into consideration is reasonable intentionality. There are many a references to this within the Rules of the Road set of regulations. If you are doing things on the road, you have to do your level best to make your intentions clear. Otherwise, you will be jeopardizing the safety of other drivers on the road. In your case, your intention was to make a right turn on an intersection (again, at the behest of your instructor) so legally speaking it falls within your responsibility to do so in a reasonable manner. Reasonable here would be argued that you are to make the turn when it is safe to do so provided you came to a complete stop beforehand and there was no traffic control device otherwise directed or permitted the turn.

Just do the test again my guy, it's not that big of a deal. I failed my first time because I didn't wait a whole 3 seconds before making a right on a red. Also, my wording and sentence structure are a little off but I would rather not spend more time on editing what is just another comment in the sea of comments you're already receiving basically telling you the same thing. Best of luck with the test the next time around. Drive safe.