Perhaps the official grounds for the exchange is b/c Lunev is 1 of the sealed indictments. If you have a high ranking ex-Russian spy working for the cabal, the odds are any cabal-approved Russian dealings like U1 are in the job description.
I was just speculating. Seems like a reasonable follow-up to the hypothesis from the last bread about exchanging Luven for Snowden with Russian to pay back the cabal.
Thanks C/M!