It absolutely is okay for him, you're right. And it's absolutely great that there is such demand for tech right now that people can afford to be so particular about their working hours and their various ways of working.
What I find less great is the suggestion that all employers should "accept your employees for who they are and optimize for their abilities" - does anyone really think that if everyone just worked whatever hours they found most pleasing, this would genuinely result in a situation that was even vaguely practical? What would happen to the people with children who actually find that working 9-5 is convenient because they get to spend a few hours with their children when they get back from work before they go to bed? Would those guys just sit around stuck for two hours in the morning whilst the night owls had a bit of a lie-in, and then have to cart the laptop around with them in the evening so they can Slack their late-working colleagues whilst they're giving the children a bath?
I don't know. Maybe I'm wrong and I'm just a dinosaur (who actually happens both to work remotely and to work strange hours sometimes too).
It obviously depends on what work there is to do. In most of what I do, I work alone, with little need for cooperation, working through the backlog of tickets to implement. And the same goes for my coworkers. So I don't know why the morning people would have to wait for the night owls or why the night owls would need the morning people to stay around late. Everyone has their own stuff to do. If I need to talk to other people, I do it between 11AM and 5PM. Or schedule ahead of time so people can anticipate.
Yes, it certainly depends on the nature of the work. If you work pretty much entirely independently (and remote work often can be like this, especially freelance), then working hours become less important - if your arrangement is that the software will be deployed by 9am Friday and all the features implemented and testable by that point, and that's your sole responsibility, no one is going to be bothered if you worked 4pm to midnight every day to do it.
I once worked with a very senior creative who was exceptional at his job. We all worked in an office together - this was a few years before the current remote phenomenon had quite the momentum behind it that it now has. He came in at midday, on a good day, and normally stayed late into the evening (I think he enjoyed having a little red wine whilst he was working, which probably slightly stretched the boundaries of acceptability in that office). His work was exceptional - on-brief but always extremely innovative. But, you know, when you actually wanted to schedule a meeting with him to discuss a project, it was always bloody hard work - he collaborated very well with the other members of his team who enjoyed staying late in the evening, but he was a constant thorn in the side of the project managers who often wanted to talk to him in the morning when he was never there.
What I find less great is the suggestion that all employers should "accept your employees for who they are and optimize for their abilities" - does anyone really think that if everyone just worked whatever hours they found most pleasing, this would genuinely result in a situation that was even vaguely practical? What would happen to the people with children who actually find that working 9-5 is convenient because they get to spend a few hours with their children when they get back from work before they go to bed? Would those guys just sit around stuck for two hours in the morning whilst the night owls had a bit of a lie-in, and then have to cart the laptop around with them in the evening so they can Slack their late-working colleagues whilst they're giving the children a bath?
I don't know. Maybe I'm wrong and I'm just a dinosaur (who actually happens both to work remotely and to work strange hours sometimes too).