The devel/json-glib port has the DOCS option explicitly stated in its OPTIONS_DEFINE. However, it does not utilize the option at all. The file contents of the packages with or without the option enabled are identical. The option should ideally be removed.
A commit references this bug:
Date: Fri Feb 12 19:54:03 UTC 2021
New revision: 565057
devel/json-glib: fix DOCS option
Submitted by: Naram Qashat <email@example.com>
The DOCS option has been fixed. Thanks for the report.