Remove DOS Charset from SMB service in legacy UI

I'm experimenting with FreeNAS 11.1-U5 and have set up a test SMB share. In the default settings I see:
DOS charset: CP437
UNIX charset: UTF-8

"CP437" strikes me as obsolete. I see UTF-8 as an option for DOS charset, so I chose that.

The docs are vague:

http://doc.freenas.org/11/services.html#smb

"DOS charset : the character set Samba uses when communicating with DOS and Windows 9x/ME clients; default is CP437
UNIX charset : default is UTF-8 which supports all characters in all languages"

So:
1) is 'DOS charset' really only for ancient OSes?
2) is UNIX charset also used for modern Windows? macOS?

Next, running 'smbstatus -b' outputs:

"ERROR: invalid DOS charset: 'dos charset' must not be UTF8, using (default value) CP850 instead."

So:
3) I guess the GUI should not even allow UTF-8 as a choice.
4) maybe 'DOS charset' should just be removed at this point (2018)?