[Proj] bug in cs2cs or what?

[vanzach at survey.ntua.gr]

Hi all.

I'm trying to convert 3 points from WGS84 to local datum and I noticed that
during the datum change phase the coordinates are the same.

$ cs2cs -f "%.4f" +ellps=WGS84 +proj=geocent +to +towgs84=-199.0,74.0,246.0
+ellps=GRS80 +proj=geocent < WGS84_XYZ.txt ; more WGS84_XYZ.txt 
4587235.7556	1964114.8816 3959354.7313
4584814.5890	1951028.4660 3968408.6021
4589128.8900	1935365.8050 3971034.4841
4587235.7556	1964114.8816	3959354.7312
4584814.589	1951028.466	3968408.602
4589128.890	1935365.805	3971034.484

Any ideas?
Thanks in advance,
Vangelis