I checked the code, and it seems to deliberately write just the first character of the atom names for XYZ output. It would be easy enough to fix, just a few lines in one source file. I could post the correction in the "Bug Reports and Fixes" forum if you'd like.
I should note that WRITE COOR XYZ does write the full atom names, but only does a single coordinate set at a time. You can create a standard DCD trajectory and post-process it via a loop over frames, but it would still be single files.