You don't even need to point the cluster members to a deployer for it to function. But, the only supported method to deploy apps to the cluster is by the use of the deployer.
You are probably getting a little tripped up in how the deployer knows it's a deployer. In 6.2 any instance can be a deployer. Mothership splunkd is always "listening" for comms from a search head cluster. And when you first bootstrap a cluster, if you point it to a instance you have decided to be the deployer, then the cluster members communicate with it to make sure it is available.