How can url-show-status be void when (featurep 'url-vars) is t?

[Lennart Borgman]

It looks impossible to me that url-show-status is void as a variable
when url-vars.elc has been loaded, but that is what I see here. Also
url-show-status seems to have been initialized by defcustom since it
has (standard-value (t)) in the property list.

url-show-status is a boolean defcustom without any :set function. So
custom-initialize-reset should have created the variable by calling
set-default.

Any ideas how then url-show-status can be void after loading url-vars?