As I put in the comments:
Frankly, I’ve generally not bothered to correct anyone who didn’t bother to research it themselves – except in the cases where they were in my own organization, and attempting to make decisions about related matters based on misconceptions of the supposed Google rule.
Of course, my dear lovely friends may have been lieing to me. I very much doubt it (and even if I didn’t, what they’ve said over the years has made a lot more sense than most of the hearsay you hear on the web) – but the point here is that I’ve bothered to ask.
Google has so many employees that if you preach on subjects like 20% time – which, by the way, I think is one of the most fundamentally important (and least well-understood) issues in corporations, job choice, and why you get up in the morning, but that’s another post – then you have no excuse at all for not going and asking an employee how it works. Last time I looked, they had bajillions of offices around Europe, not to mention the sprawl all over the US.