All the hipster programmers want to work whenever they please as well. Come in at 10-11 and stay to 8-9. They get about 3 hours of face time with experienced coders and wonder why their latest “I got it from a blog” doesn’t work.
Some work is less tied to a schedule that other work and I don’t mind a flex schedule so long as it’s getting done and not causing a bottleneck or holdup. If it’s tied to a schedule and absence would cause a problem then the employee needs to be punctual and not fail to show up without notice. That’s really not too much to expect.