pfctl.8: Further document recursive flush behaviour

OK sashan

Obtained from:	OpenBSD, kn <kn@openbsd.org>, 5bd1c2906f
Sponsored by:	Rubicon Communications, LLC ("Netgate")

sbin/pfctl/pfctl.8

@@ -24,7 +24,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd July 4, 2025
+.Dd July 7, 2025
 .Dt PFCTL 8
 .Os
 .Sh NAME
@@ -238,6 +238,19 @@ for details.
 .It Fl F Cm all
 Flush all of the above.
 .El
+.Pp
+If
+.Fl a
+is specified as well and
+.Ar anchor
+is terminated with a
+.Sq *
+character,
+.Cm rules ,
+.Cm Tables
+and
+.Cm all
+flush the given anchor recursively.
 .It Fl f Ar file
 Load the rules contained in
 .Ar file .