[ORD/CE] _USTN_WORKSETDGNWS

I am trying to understand this variable.

I would think it needs to be defined somewhere, but my attempts to define it don't seem to be working.

In this thread, Marc Thomas says he uses
_USTN_WORKSETDGNWS = $(_USTN_WORKSETSTANDARDS)$(_USTN_WORKSETNAME).DGNWS
%lock _USTN_WORKSETDGNWS

I'd like to do something similar except to save it directly next to the workset CFG more like
_USTN_WORKSETDGNWS         = $(_USTN_WORKSETSROOT)$(_USTN_WORKSETNAME).dgnws

But it doesn't matter what level I define that variable at, whether I lock it or not, it doesn't define correctly. The _USTNWORKSETNAME part always goes missing.

For example, I select a workspace, select a workset, open a drawing and exit ORD just to make sure that everything loaded all the way before I run my MSDBUG -5.
In the MSDEBUG.txt and the end where it shows the final complete definition of the variables, I can see

_USTN_WORKSETSROOT  = M:\Bentley\ORD\Configuration\WorkSets\
and
_USTN_WORKSETNAME  = INDOT_Test

I would think this should resolve _USTN_WORKSETDGNWS to  M:\Bentley\ORD\Configuration\WorkSets\INDOT_Test.dgnws
Which would be correct. Instead, I see

_USTN_WORKSETDGNWS  = M:\Bentley\ORD\Configuration\WorkSets\.dgnws 

It doesn't matter if I try to define this in WorkSpaceSettings.cfg or my Organization.cfg or even the workset.cfg.
And if I don't define it anywhere, that variable doesn't appear to get defined at all.

Any clue what I am doing wrong?