I tested with 7.3.7 and now I can confirm that this is broken in 8.x:
filer1-1-co> exportfs -io sec=none,rw /vol/t
cn1:~ # mount filer1-1-co:/vol/t /mnt
cn1:~ # touch /mnt/foo
cn1:~ # su - tele
tele@cn1:~> touch /mnt/bar
tele@cn1:~> ll /mnt
total 0
-rw-r--r-- 1 nobody nogroup 0 Jul 19 12:22 bar
-rw-r--r-- 1 nobody nogroup 0 Jul 19 11:52 foo
While on 8.2 I am not even able to mount it. Of course, I also have different host OS here (RHEL vs. SLES) but as I get error reply from Data ONTAP I do not think it depends on client.
I do have a case open with NetApp support for over a week now, and so far they had zero luck fixing the issue (that's basically the point where I turned for help to community).
I do not mean opening case and asking "how to implement all_squash". I mean opening case about sec=none being completely broken in 8.x. May be there is already bug about it in this case the more people complain the more chances it gets fixed.