Because I do not use XML reports myself, I was unaware of what you pointed out, Josk. And I've only been able to have the briefest of conversations about this 'quirk', and will post later when I able to get more information.
However it turns out that it is not a glitch, but a conscious decision (based on advertiser feedback) behind the format you see. Essentially the intent was to add greater precision for high-level users who want it.
One person that I spoke with, known for a quick wit, said: "After all, who wouldn’t rather say “eight hundred and fifty thousand one-millionths of a dollar” instead of “eighty-five cents”?
Your feedback on this is welcome, and I'll certainly pass it on to the right folks.