It's a horrible law, and you can tell it's been festering in a Frank Luntz laboratory for some time (seriously, it reminds me of social security privatization). "Workplace flexibility" would instead give employers an easier ability to cut overtime compensation. Federal workers tend to have stronger union benefits (and more friends in Washington) than private sector folks. A business could therefore abuse this law to force or "encourage" workers to take paid time off instead of OT. Unions would then step in...but oh wait, they're being systematically dismantled.
Kill unions, cut benefits, and then act oblivious when the working class gets screwed. It's a pretty transparent pro-business attack.
I've got a better idea. Raise the minimum wage and increase vacation time. I seem to recall US businesses are currently sitting on trillions of dollars.