By running the job ConvertExternalUserOnStartDateJob the username of the SF user is updated to contain the value of the userID.
SAP SuccessFactors Onboarding
Currently as per the system behavior if the username is not visible during Manage Pending Hires then post conversion we update userID as username. This is expected system behavior.
Enable the Username field from Manage Business Configuration for it to be visible in Manage Pending Hires step. Post this the username will not be updated to userID when ConvertExternalUserOnStartDateJob runs.
ConvertExternalUserOnStartDateJob, username, userID, Manage Pending Hires , KBA , LOD-SF-OBX-JOB , Conversion External User to Internal User , Bug Filed