Why is it that when I create a Order Base from PostMan with IsShippable flag ‘Y’, it don't release?

• Why is it that when I create a Order Base from PostMan with IsShippable flag ‘Y’, it does not release( create order release) but when I create a Order Base using UI with exact same data it release(creates order release).

Is this the general OTM behaviour or there is something that needs also to be checked for this behavior through PostMan to be same as UI?

NOTE:- There are no Automation Agent which is triggering on Order Base/Order Base Ship Unit Creation either through UI or via. PostMan. Also, same data is there in both Order Base.