Status of original non stock purchase order line bumped back from 280/281 when a change order is add

Hello All,

In an ongoing scenario , a user adds a change order to an existing non stock purchase order only to find that the status of the original order line is bumped back to 281-230  and both the lines are routed for approval.

The status flow is as:-

220-230 : PO entry

230-230 : PO stuck for approval

230-280: PO approved

280-281: Print purchase order

Line type used is 'B' with inv interface = 'B'.

Is this standard system behavior to bump the status of original order line also to 281-230?? Can this be controlled by activating Base order protection in processing options#7.4???