This seems a bit off to me. We're used to scanning things, specially after doing something more than once and since I already know what I want, I can click on the OK button as soon as I see it. No back-tracking needed.
I think the difference is optimization for first use and subsequent use... but thing is, we've all seen OK/Cancel prompts before.
It's interesting to think about common patterns and if they really are in the user's best interest or if a new pattern might offer some benefit. I'm undecided in this case.
When it comes to non-standard button labels, when there are more than 2 options, or on dialogs where the user should think about what they are doing (e.g., actions which cannot be undone) having the most used option last doesn't sound like the worst idea.
I think the difference is optimization for first use and subsequent use... but thing is, we've all seen OK/Cancel prompts before.