In RCM implementation guide Section 10.8 Candidate Profile Extension, it is stated that "If the candidate, who is anonymized, is linked with secondary candidates, any Candidate Profile Extension on the secondary candidate profiles will be deleted along with their audit data".
Note: This is applicable only for merged candidates.
SuccessFactors Recruiting Management
Secondary candidate means the legacy candidate data that has been discarded after the candidate merge. This data is not longer visible in the UI and it will be anonymized once the candidate purge takes place.
candidate profile extention; secondary candidate profile; candidate profile , KBA , LOD-SF-RCM-CAN , General Candidate Issues (not Offers, not Profiles) , How To