From initial iterview of the controller it followed the aerodrome warned the aircraft that they are way below the gliding path. That initially they were going "very steady" but then began losing hight rapidly for the reason unknown to the aerodrome.
Can be the controller saw them somehow on own screen otherwise how would he know? Unless the crew kept giving the controller its own idea of their height?
Since investigation committees took over - apparently the controllers were prohibited to talk to the journalists, and only as much is known as got out in the first day during the general rush and ran around.
Confirmation of the contents of the talks ground-aircraft are in the black box record - delayed and delayed to be made public. Besides, there was a small article in Polish media that the Polish Defence ministry monitored the whole flight, its location and route throughout, and has records as well - of talks in the pilot cabin. But that the Defense Ministry only aknowledges they have all that but doesn't plan to let it known publicly.
The only leak of the content of the talks was in Russian internet, listened to, in Russia, approx.? already 5? days ago. And the only thing the man who listened to it shared was that "they would have landed come anything - cows on the runway or Virgin Mary standing on the runway herself". And that at one point the commander asked "Are we on time?"
That's absolutely all that was available from un-official sources.
And official ones keep it to themselves.