Are you all sure that NATO planes always fly with transponders ON? I am not. It is often (not always, to be fair) specially underlined in reports that transponders were off.
What about these talks 4 years ago?
https://www.wsj.com/articles/nato-re...ion-1474391644NATO Rejects Russian Air-Safety Proposal for Planes in Baltic Region....
WSJ seems not to be a pro-Russian fake news agency.....