Extended_bounds causes extra bucket


I am using date_histogram to get data in buckets grouped by time. Interval is weekly with offset of -1d, and time_zone is +08:00. The min value is equal to the "gte". When using extended_bounds, I get an extra bucket for the week before if the query starts on Sunday.

My guess is the offset is not being accounted for in the extended bounds. Is this the case?