Your scenario still uses a centralised single postgres server. Failure of that server takes down the whole locking functionality. That's not what people usually mean by "distributed".
"the machines involved can fail" must also include the postgres machines.
To get that, you need to coordinate multiple postgres servers, e.g. using ... distributed locking. Postgres does not provide that out of the box -- neither multi-master setups, nor master-standby synchronous replication with automatic failover. Wrapper software that provides that, such as Stolon and Patroni, use distributed KV stores / lock managers such as etcd and Consul to provide it.
"the machines involved can fail" must also include the postgres machines.
To get that, you need to coordinate multiple postgres servers, e.g. using ... distributed locking. Postgres does not provide that out of the box -- neither multi-master setups, nor master-standby synchronous replication with automatic failover. Wrapper software that provides that, such as Stolon and Patroni, use distributed KV stores / lock managers such as etcd and Consul to provide it.