It shouldn't be referred as Terrain Radar. It's mistakenly named as a radar because it has a re-draw sweep. I still remember the first time I got in a flight deck and pushed TERR. I asked my instructor how come we can activate this radar, but not the radar while parked at the gate. My instructor answered briefly that the EGPWS is not radar. It just uses a re-draw sweep engine to display the terrain data. So yeah... it's a mistake almost all of us make.