advice needed . pls ,ee2, NRM

MY best friend applied for her younger brother , recieve coa with right to work, he got a jobs with it , he is till working there , later recieve a method of qestionair , which was fill and send to HO, but the problem is , his method of entry was by agent , now got a letter from HO, asking him to sign if he want his case to be consider under national referral mechanis , which i suggested no, to my best friend , the problem is am giving my friend the right advice for her younger one , is he going to be refused if he sign no to the referral machanism?
advice needed, pls