As a user, there are times when I don't wear my sleep tracker to bed, but I nonetheless want to record my sleep times.
Apple Health supports this with the "Add Data" feature, but it's not possible to provide a time zone in the form.
Then as a developer, user-added sleep samples are missing time zone information.
I would expect that the time zone is requested within the Add Data form.
Without this information provided at input time, downstream applications are forced to infer the time zone ourselves, leading to potentially buggy or unintuitive behavior.