Why does bottom up scheduling not consider the resource usage split

We use Workday calendars and shift patterns in eAM, based on which the resource usage is split on the WO.

Once the WO is firmed, system allows me to change the resource header dates and triggers bottom up scheduling if WO resource dates are outside of the Operation/WO dates.

This however does nothing to the resource usage dates where I can still see resource end times outside of the parent records. is this a bug or by design?

Example:

WO1 created with Op1 and Resource1 with required duration of 6 hours.

Shift time is 07:15 to 12:00 and 12:30 to 15:30 hours

WO1 scheduled to start at 7:15 so splits resources in 2 lines