It is expected behavior. This is documented in note: Does Order Import Import Partial When Some of the Order Lines Errored Out ? (Doc ID 2242172.1)
As per current functionality, if there is any error on any of the order lines,
then the lines inserted into OM base tables will be rolled back and the whole data exists in the interface table showing the errors.
There is an open ER Bug 1689934 : ALLOW PARTIAL IMPORT OF ORDERS IF SOME LINES FAIL VALIDATION
This ER requests parameter / setup to allow order import to import some of the lines.
Thanks Avanti for your response.