Oh, that was on purpose, believe me. There is one section where I use "standard" units before metric, but now I don't remember where. It's because miles were more convenient, since I was referencing some common knowledge "fact" usually quoted in miles.

I prefer metric, though I still think in miles. It's impossible to use metric in daily life still, but I try to squeeze it in when I can. In interviews, I always try to use both.