On 6.3.0/6.3.1/6.3.2, I've noticed files I create on the Mac through a samba share are sometimes ending up on the unRaid server with odd permissions:

 

$ touch /Volumes/cache/hi
$ ssh tower
$ ls -lart /mnt/cache/hi
-rw-r--r-- 1 jaiken users 0 Feb 13 18:00 hi

$ exit
logout
Connection to tower closed.

$ chmod -r /Volumes/cache/hi
$ ssh tower
$ ls -lart /mnt/cache/hi
--w------- 1 jaiken users 0 Feb 13 18:00 /mnt/cache/hi

 

Isn't it supposed to automatically `nobody:users` and set all the permissions for you?

That's the way AFP has always worked if you connect to the share as a registered user. If you connect as a guest user then a new file is owned by the nobody user. Perhaps SMB has been brought into line? What are you showing in the lower part of your example? chmod -r removes the read permissions, as shown.