He says he was a cooperating witness in an FBI investigation or some Russian businessman...that doesn't make him an FBI employee.
In fact it sounds like he was originally a target in that investigation.
If the FBI themselves admits he was an Undercover Employee and he then confirms it, I see no room for doubt
in May of 2016 he was an Undercover Employee of the FBI and in October he was a dangerous spy threatening National Security, and he has still not been arrested or charged.
The FBI obtained the recordings after Sporyshev attempted to recruit an FBI undercover employee (“UCE-1”), who was posing as an analyst from a New York-based energy company.
Cooperating witness can mean a deal has been made not to prosecute the witness of something they found. Blackmailing for favors leaves no paper trail.