This isn't necessarily true but I see where you're head is at. It's very hard to farm honor right now on Onyxia because people simply aren't queueing enough. You'll get queues, but during non-peak hours and sometimes even during peak hours, you're just waiting for queues to pop and are spamming global to 'Queue AB'.
If you really tried, you could get cap but it takes a lot longer due to wait times. This lackluster PvP scene post-hype of launch is what the staff has stated they're trying to avoid.
Again, in my POV, if Onyxia players had a thriving PvP scene that cares so much about the changes being implemented, we would see them logging on to play and get honor cap. But we aren't seeing that. People are logged until TBC.
This influx of PvP-only players into the PvP side of the ecosystem will keep queues short when these players DO decide to play whether for fun or to push, even late into the expansion, and keep variety in arena across all of the ranges of mmr/cr.