I did not think this was a bug. If you do an lsof (list open files) on the files, you can get the process ID that "owns" the files. Typically it is a process that is still running.
I assume he meant that there are cases in some Solaris 2.x releases where either
1) a file *isn't* in use, but the NFS client code *thinks* it is, so attempts to remove the file get turned into attempts to rename it to a ".nfs" name;
2) if a file was in use, and an attempt to remove it got turned into an attempt to rename it, when the file ceased to be in use the NFS client code didn't realize this and remove the ".nfs" file;
or something such as that, so that you get ".nfs" files when you *shouldn't* get them, or ".nfs" files don't get cleaned up properly (not due to a client crashing before it has a chance to clean them up).