I’m with you on this one.
Had a friend that did some nuclear material recovery work in a former republic acouple off years after the fall of the Soviet Union. Local security was being provided by a company manned entirely by ex-Spetnaz that had been originally recruited from that locale. In conversation with them, my friend said that he found out 2 things:
1) The guards had detailed knowledge of US cities and locations indicating they had all spent significant time in the United States learning about US geography, politics, society, etc. and
2) All the conversations were in unaccented, standard Mid-western dialect with plenty of properly used American slang thrown in.
In other words, they had been trained to convincingly pass for Americans as part of their mission preparation.
The detained “US mercenary” is Russian Spetnaz pretending to be one.