I agree. In my experience, "flexible work hours" is often code for "everyone works weird fucking hours so instead of having a set routine, you have to be quasi-available at all times to respond to the person who decided to wait until 8pm to do the work you were waiting on". It's great for the person who needs flexibility, and shitty for everyone that depends on that person.

Flexible working arrangements are great when the team is able to asynchronously work, but I have yet to see a team that really does asynchronous work right.