How to lock the current allocation state

When cluster.routing.rebalance.enable is set to none, I understand that we are lokcing the current allocation state of the cluster. i.e. the currenlty allocated shards will not relocate to other nodes.
But what happens is a new index is created? will its shards remain unassigned because allocation.enable is set to none?

Can I ask what problem are you trying to solve with this approach?