#FreeBSD #NFS discovery of the day:

Some things depend on nfsv4_server_only in rc.conf.
Some things depend on vfs.nfsd.server_min_nfsvers at the time the daemon starts up.
Some things don't care about either, which is how you get rpc.lockd running on your v4-only file server, or mountd running in v4-only mode even though rpcbind has a v3 service registered.