I don’t know. I was curious about it, too.
I saw the F-35, F-16 and several F-4 ones when I was looking for Soviet intercepts. The point is that this happens all the time and seems to only be a news worthy story now that the commie press hates the commie Russians because it helps their phoney narrative against Trump.
I remember many years ago, the U.S. got Canada to scrap a very advanced fighter, the Avro Arrow. The reason was the program was chock full of Soviet spies. The plane was so advanced that we did not want the Russians to have it.
In exchange we gave them a bunch of F-101s.