It’s incorrect to say that Arch/Viz as a category of work is royalty free. The question is whether the work falls into one of the royalty exemptions listed in the EULA. Nearly all of the time with Arch/Viz, that’s the case.
If you are doing custom work for a single client, those work-for-hire fees are royalty free. If your client doesn’t commercialize the work you do for them, there’s no royalty there either. I know this is an unlikely scenario, but if you created a custom 3D building walkthrough for a client, there’s no royalty. But if your client went and sold that walkthrough on the iTunes store, there would be a royalty. I imagine this is never going to happen, but I use it to illustrate how the royalty terms work.