Comey tried to set himself with a lesser charge that could be contested. Barr didn't bite.
Say Comey got caught stealing jewelry with accomplices. He sets himself up for a charge of lock picking, but it also could have been his accomplices. Comey skates on lock picking and that makes it looks like the jewelry theft was a bum rap. too.
That's the way I read it. Cut out charge? He takes a part of the crime out that's easy too defend and has it tried separately.