It'd be strange if this remains the case (that ATC can't see SE2 transmissions).
(And even more strange that we don't have clarity on it by now, one way or the other.)
This was written back in 2021 in Flight Safety Australia in an article called "VFR and Visible"
Can ATC ‘see’ my SkyEcho2?
The prime objective of SkyEcho2 is air-to-air traffic awareness – the device is not certified to the performance standards needed for ATC separation services. Nevertheless, CASA envisages the device being used for situational awareness by ATC.
By early this year, the Airservices Australia ATC system had not been modified to display SkyEcho2; however, it is expected that with a new ATC system on the way, SkyEcho2 transmissions will be displayed to controllers, for situational awareness only, using distinctive symbology which will prevent the application of surveillance separation standards to those aircraft. Given the COVID crisis, there is uncertainty about when this capability may be delivered by Airservices Australia.
VFR and visible _ Flight Safety Australia copy.pdf