You can tell your coworkers to shove it and probably should in this scenario, I think the more pressing matter is that realistically you are free to set your hours freely between 6:00 to 21:00 except you have to be there from 9:00 - 15:00 or some other six hour chunk as a "core time".

Does give you some options but the only real flexibility you get out of it is you can put some more overtime in if you want