These days, devel/subversion is always built with gnome-keyring and kwallet support disabled. This means code such as svn_auth_get_platform_specific_provider() in subversion/libsvn_subr/auth.c never call the functions in the plugins because SVN_HAVE_GNOME_KEYRING and SVN_HAVE_KWALLET are off in subversion/svn_private_config.h, and so even if subversion-kwallet (or gnome-keyring) are installed they are not used for authentication.
A commit references this bug: Author: lev Date: Mon Jun 30 14:24:05 UTC 2014 New revision: 359849 URL: http://svnweb.freebsd.org/changeset/ports/359849 Log: Fix KWallet / GNOMe Keyring integration: eanble code in "main" libraries as it doesn't call any functions from KWallet/Keyring directly but should be enabled to load plugins dynamically. PR: 191463 Submitted by: Raphael Kubo da Costa Changes: head/devel/subversion/Makefile
Fixed, thanks!