Climate does play a role in this, if you're in a hot climate they need to be able to access water first thing in the morning (if it's outside) and/or need to get out of the coop before it gets too hot, if that's an issue.
If heat isn't an issue, then they technically can be let out well past sunrise if that's your preference, as long as there's enough space inside for them to move around in and not pick at each other. My coop was built to provide 4 sq ft per bird (though they have a bit more, as I haven't maxxed out capacity. )My auto door is set for 7:45 AM year round because we get a lot of potential predator activity right around sunrise (my run is next to a creek), and because it keeps them slightly quieter since we wake up an hour past that.