Hello Rudi
CA strictly adheres to Support Matrix adoption. If it suggests in the Support Matrix that OUD11g isn't supported for Password Services and AdminUI Store - it means CA hasn't certified these functionality with OUD 11g. Thus CA would defer customers from using OUD11g for those functions.
Should you choose to use it, and any issue arises - It would be a conflict of interests and is not a good position to be in (one as a Customer and other as a Vendor). The very first point of contention would be "it is clearly stated unsupported, then why was it used in that particular unsupported form".
The best way would be to raise an ER in the communities ideation site and have it pursued via your CA Account Manager to be delivered (Have OUD 11g Certified Officially to be used with Password Policy and AdminUI Store) as per mutually agreeable timelines. This is applicable to anything that is not present in OR states to be unsupported in the Support Matrix.
Regards
Hubert