And what is gained by doing it this way versus shifting the hour hand?

Clocks update themselves. Store hour signs, bus tables, stickers in windows, business cards, Outlook calendars, etc. They do not.

I don't like changing clocks twice a year; sticking with one time-zone offset is better. But having the entire population shift their working, banking, classroom, and service hours ad hoc is strictly worse than a universal hour shift. Instead of "Open M-F, 9a-5p", you suggest that "Open M-F, 9a-5p, Winter, 10a-6p Summer" is more elegant? Because that's what all vinyl stickers on glass doors would look like.

And it's still centralized and regulated, just like DST is now. So what have we gained?

Also you'd have to agree on how to define "winter" and "summer", just like we now have rules that guarantee that all daylight savings time changes will be on the same date across all US states or EU countries.

Seasonal schedules is already a thing in many places. It's not that hard.

No. But neither is changing the clock. So what’s the benefit of having enforced seasonal schedule changes vs the DST change?

Forcing it would only be temporary to make the transition smoother, getting people used to updating schedules. After the first two years or so, it would hopefully run on its own, people would run on the schedules that makes sense locally.

Asking again: What’s the benefit of having enforced seasonal schedule changes vs. the DST change?

Having a rational clock

There's more examples like this, famously electric negative and positive poles that would have been reversed compared to the current standard if the scientists would have known how things work.

Many current standards have unintuitive quirks that only live on because they're old and entrenched, and that wouldn't have existed if the standards were set today instead.

So let's stop with the dumb quirks before it's entrenched.

Every meeting in every outlook calendar in the country would have to change. Every exchange (equities, derivatives, commodities, etc) would all have to revise their trading schedules and applications, all the trading systems connecting to them would have to change and in some cases the actual laws governing those exchanges might need to be updated. The work contracts or at least the conditions of employment of millions of people would need to be changed. I've worked on applications that need to connect on a schedule to end points in other timezones, and plan and implement time and DST changes. It would be a nightmare.

Decide on the switch a few years in advance. Nobody would need to instantaneously change any schedules, just to remember that after a certain time in the future it will need to be updated.