AbstractSimhon et al. (2016) proved that disclosing queue length to customers when the queue is shorter than some threshold and concealing the information otherwise cannot maximize the throughout of M/M/1 queues—when customers are familiar with the policy and the threshold. We show that said policy indeed maximizes throughput when customers do not have information of the policy. Furthermore, we prove that the socially optimal disclosure policy under this setting contains a “hole,” that is, it is socially optimal to disclose queue length to the customers when the queue is sufficiently short or sufficiently long but not disclose otherwise.