How does that make it easier though? If I have the out of band knowledge that 9-5 is standard business hours, all I need to know if I'm organizing something across time zones is when our UTC offsets are.
If there are no timezones, I don't have the out of band knowledge of what standard business hours are, and I need to somehow figure this out for all parties. Abolishing timezones makes some computation tasks easier, at the expense of complicating actual human interactions.
So the argument is that "getting up at 9:00" is equally worthless in such a situation for connoting waking up a little late. Especially in a place with no sunlight, where the hour when you get up is all the more arbitrary since you don't have the sun to provide a natural guide.
> Businesses will center their schedules around this window no matter what it's called.
The original point is that a business's customers are rarely all in the same time zone anymore. Abiding by UTC doesn't prevent them from opening mainly during the daytime, it just makes it easier to do business with people who live that much further away from you. The point about social tyranny is more a side benefit than the main argument.