When is a backordered line reset to Ready to Release?

My question is with respect version 11.5.10.

It was found that a delivery detail that is partially backordered during Pick Release is reset to Ready to Release status. Do backordered lines get reset to Ready to Release status at a later point in time? If so, what triggers it?

A specific test example follows (in sequence):

1) Order 7663/Line 2.1 has open qty 2600.

2) Autocreated WIP job 516228 for the above order line.

3) A quantity of 2000 completed on the WIP job. 600 remains to be completed.

4) Split Delivery Detail 267748 (belonging to the above order line) into two, for quantities 300 and 2300.

5) Launched Pick release for the DD of qty 2300.