Originally Posted by
marie paire
This is not so. The ATC tag will show the altitude the aircraft is cleared to (controller manual input processed by the ATC FDPS) and the actual FL and attitude of the aircraft (climbing, descending, level) derived from mode C.
No, the OP is correct, at least for those Mode S radars that interrogate for downloadable parameters (DAPs).
The controller gets to see the SELECTED altitude. The whole point is that, by comparing that to the CLEARED altitude, the controller gets an early warning of a potential level bust where the two values aren't the same.