The tree(2) man page mentions neither the RB_FOREACH_SAFE() nor the RB_FOREACH_REVERSE_SAFE(), yet they are clearly included in /usr/include/sys/tree.h. Not a problem for anyone familiar with the API, but useful to those reading man pages to understand the scope its scope and capabilities. Also, good for completeness :-)
For bugs matching the following criteria: Status: In Progress Changed: (is less than) 2014-06-01 Reset to default assignee and clear in-progress tags. Mail being skipped
Looks like the tree(3) man page now documents the the "safe" APIs (in FreeBSD 11.2) so this ticket can be closed.
For the record, it was documented in r257643 with merge to stable/10@261015 (before 10.1). Thanks for the report.