MAKUNBOUND vs. special binding

[David A. Moon <Moon@STONY-BROOK.SCRC.Symbolics.COM>]

I believe the problem here is just the unfortunate use of the word
"bind" to mean two different things.  (1) A variable is bound to
a value when evaluating that variable produces that value, and is
unbound when evaluating that variable is an error.  (2) A special
variable is bound when its value has been saved upon entry to a
dynamic extent, and will be restored upon exit.  This poor use of
English seems to date back to the earliest days of Lisp, as far as
I can tell, but maybe it's time to deep-six it.

MAKUNBOUND refers to definition 1.  Thus the answer to your question is
the innermost binding (definition 1) is undone, while the innermost
binding (definition 2) remains unaffected.