That's not true. Anyone has access to 20% time, the question is just whether or not it makes sense for individual people.
Source: I work here and take advantage of 20% time.
I have to ask out of curiosity: with Google having over 50,000 employees, are you in a place to say 'anyone' (sure, we're talking about developers, but still)?
Only because this question has been asked multiple times at TGIF (regular all-hands meeting).