Hi, It looks to me that the -Y option is used to specify the destination to which to send synchronisation messages (not where to receive them, this is -y).
Index: dhcpd.8 =================================================================== RCS file: /cvs/OpenBSD/src/usr.sbin/dhcpd/dhcpd.8,v retrieving revision 1.29 diff -u -p -u -r1.29 dhcpd.8 --- dhcpd.8 29 Aug 2017 08:20:18 -0000 1.29 +++ dhcpd.8 22 Feb 2022 15:45:20 -0000 @@ -252,7 +252,7 @@ the limited broadcast address (255.255.2 .It Fl Y Ar synctarget Add target .Ar synctarget -to receive synchronisation messages. +to send synchronisation messages. .Ar synctarget can be either an IPv4 address for unicast messages or a network interface name followed optionally by a colon and a numeric TTL -- Matthieu Herrb