Yes China should have some of this, but they have also had time to adapt to a fixed timezone.
Most of these curves are U-shaped...
I think generally standard time-1 would "hurt" early birds, and DST/double DST would discriminate against night owls.
The pattern for early birds is they get an invite for a business dinner at 9PM (staying up late) and then they wake up at 4:30AM anyway, so they don't sleep enough when you make them stay up late.
