It is possible when booking through the Orbitz engine on the RBC Rewards page to find some fine print on branded fare and booking class, at least from what I remember last time I did an online Avion booking a few months ago. I have NEVER had a problem with an online Avion booking not being credit for AQS/AQM, though obviously if you read through the thread there are many cases of this happening.

I now almost always call RBC Rewards to get a "statement credit" and book directly with AC. This allows me to book a right up to the maximum base fare, e.g. Flex and once even PY on a Europe redemption. Recently the phone agents have tried to tell me it's not possible - they relent when I say that I need different booking classes for outbound vs return. The only annoying thing is that you end up on the phone forever while they say their spiel about the statement credit process. But this is seemingly the only way to guarantee no problems with AQS/AQM.