Hi All,
I debugged SU01 and discovered the answer is in vanilla NetWeaver functionality, and I'm guessing what has happened is someone has added an entry to the table USR_DBMS_SYSTEM, and not realised that this will then trigger the process as described in this post (wish I found this reference when I was looking into replicating users into HANA in the first place).
DBMS Users in SAP NetWeaver AS ABAP 7.40
Thanks BJ and Amar for trying to help me get to the bottom of this.
Cheers,
Matt