I still think Flynn lied to the FBI. Maybe it was a simple misstatement based on a bad memory. They asked him if he talked to Kislyak and he said no. The FBI had already heard recordings of Flynn talking to Kislyak.
I think this is one of those situations that Flynn is guilty of the letter of the law, but not the spirit. He wasn't colluding with Russia. He wasn't doing anything illegal or unethical. The FBI did deceive him. Called him in under false pretenses.
That is why he was able to get his case dropped. Even with the lie and the guilty plea, the government didn't have much of a case.