Solution : https://service.sap.com/sap/support/notes/1618942 (SAP Service marketplace login required)
Key words : 
template based request, terms access control 2010, multiple users reason, multiple users, symptom create, step review, user selection, hidden fields, prerequisites code, solution implement
Related Notes : 
       
| 1616486 | UAM : User details are editable in template based request | 
| 1607067 | Master Note for SAP Access Control 10.0 - Support Pack 6 |