I just found the following line in /usr/share/applications/grass64-grass.desktop:
Exec=linux -T Grass -e /usr/bin/grass64 -wxpython
often I found something like:
Exec=dump -T Grass
I have the feeling, that this is a bug or can give me anybody an explanation of this behaviour?
Closing as OBSOLETE - sci-geosciences/grass-7.0.1 has been added to the tree as per bug 514514 and subsequently revbumped. Note that sci-geosciences/grass:6 has been masked and will be removed from the tree in the coming weeks.