Yeah, that's where I went from "this could be useful" to "that's stupid". It's like doing an internet speed test to determine how long it will take to download a file, ignoring how fast the file has actually been downloading.
It's one thing to calibrate, it's another to rely on context-sensitive data and pretend it is universal, when instead you can just rely on the context-specific data for any specific context and refine the estimates as you go. To my knowledge, web browsers do not "calibrate" like this.
