WITH_BDB_VER=..., since r365599, gets prioritized over USE_BDB, where it used to be ignored when it was in conflict with USE_BDB. Relevant list posts: https://lists.freebsd.org/pipermail/freebsd-ports/2014-August/094916.html https://lists.freebsd.org/pipermail/freebsd-ports/2014-August/094941.html
As far as I can tell this has been fixed.