Could this be the boat they launched secretly? The one we knew nothing about until it hit the water?
Elint is still a possibility. We don't know how much they gleaned from our aircraft. Three years is enough time to implement.
One more thought; it may be actively comms disruptive based on the same info from our aircraft.
Thats a distinct possibility.
They seem to have 1980's era gear on them and are roughly equivalent to our old Permit class submarine's, except they are seriously loud.
The French helped the Chinese put them together, so they cant be much. Wonder how well they would stand a depth charging..LOL