Interesting, I didn't know that but then again I don't use TOR, it's slow af for me and I don't see the benefit when most exit nodes are NSA from what I read...
TOR is made up of several circuits. The exit node doesn't know where the original message came from and who sent it unless the same party also controls the entry node. So in theory, you should be safe if you use ONLY an NSA controlled exit node, but not an NSA entry node.