No, it's not the use of proxy that saves his bacon, it's that the people doing the classification did so after the fact, and saw to it that none of the material Comey gave to Richman to give to the NYT could be a criminal leak. The people doing the after the fact classification review were Strzok, Page, Rybicki, and one other "inside the coup" player.
Singling Comey out for the common practice of FBI leaking (when caught, inevitably prosecution is declined) would in fact be selective prosecution.
DOJ Declined to Prosecute Deputy Assistant Director of FBI Who Made Illegal Leak - May 31, 2019
Misconduct at Justice Department isn't always prosecuted - September 10, 2014
FBI Use of Exigent Letters - January 2010 (illegal spying on citizens)
OVERSIGHT: RESTORING CONFIDENCE IN THE FBI - June 2001 (FBI has been totally corrupt for a long time)
It's good to be king.