defvar in SKILL++

From the SKILL Language Reference:

defvar( 
s_varName 
[ g_value ] 
) 
=> g_value | nil
 
(SKILL mode only) Defines a global variable and assigns it a
value. Use the define syntax form to define global variables
in SKILL++ mode.

The "SKILL mode only" qualifier makes it sound like you get undefined behavior in SKILL++.  What you actually get in SKILL33.00 is the usual lexical binding, as with define:

ILS-> (defun foo (x) (defvar y 3) (times x y))
foo
ILS-> (foo 2)
6
ILS-> y
*Error* eval: unbound variable - y

The sentence, "use the define syntax form to define global variables in SKILL++ mode," seems to be more of a coding style recommendation than a technical limitation, since define and defvar are essentially identical in SKILL++.  (Also, neither define nor defvar bind in the toplevel environment unless they are evaluated in the toplevel environment.  The description almost makes it sound like you can use define like defglobalfun--a sort of "defglobalvar".)

So when it says "SKILL mode only", is it really saying that the dynamic-scope semantics you would expect from CL are only available in SKILL mode?

Or is it saying, "don't depend on the current behavior of defvar in SKILL++ mode, because we might change it someday"?

Also, why isn't the third argument (the docstring) documented?  What happens if you provide a docstring?  It would be cool if you could use defvar to provide finder-style documentation!