Fridays can be "lame duck" days, and I never start something new over after noon. So Fix it Friday is a good way to allocate smaller blocks of time for smaller tasks.
But 20% is about side projects. Meeting Free Monday could be a good policy to foster those.
Yeah, my manager love his job and works 12-14 hours a day. I have to push back often on Friday to say "I'm out", he's always cool with it but he tends to forget what day it is so I have to remind him. It's on reason I stick with the well paid consultant by the hour work. I like programming but it's not my sole reason for existence. The only reason I still like it is that I survived a burn out job and realized that I didn't hate programming, I just hated not having a life because I was working such long hours and had no energy for other things.
But 20% is about side projects. Meeting Free Monday could be a good policy to foster those.