It's possible Halper may have been dangling names to see if Papadopoulos took the bait.
Halper ping.
Halper hosted Trubnikov at two intelligence seminars at Cambridge in 2012 and 2015, and interviewed the former Kremlin insider for a 2015 study on China-Russia relations he did for the Pentagons Office of Net Assessment (ONA).
And if other story's accurate, Trubnikov was close to Primakov.