How is “ʿan ʿAbd Allāh” identified in this report?

The Prohibition on Relating Everything Heard: Verification, Selection and Audience

• The commentary identifies him as Ibn Masʿūd
• The name is intentionally unidentifiable
• It refers to ʿAbd Allāh b. al-Mubārak
• It refers to Khubayb b. ʿAbd al-Raḥmān