I sent this to bugs@ a while back, but it seems to have been missed. smtpd-filters.7 is not installed by default.
--- usr.sbin/smtpd/smtpd/Makefile.dist Wed Apr 21 04:54:10 2021 +++ usr.sbin/smtpd/smtpd/Makefile Mon Oct 25 11:54:39 2021 @@ -76,7 +76,7 @@ SRCS+= stat_ramstat.c -MAN= sendmail.8 smtpd.8 smtpd.conf.5 table.5 +MAN= sendmail.8 smtpd-filters.7 smtpd.8 smtpd.conf.5 table.5 BINDIR= /usr/sbin LDADD+= -levent -lutil -ltls -lssl -lcrypto -lz