Nested Resources - Unable to Resolve Names

[sol3uk]

Describe the bug
Forgive me if I'm doing something wrong, but I've noticed a lot of our templates will fail to display the names correctly, even when parameters are provided. Turns out this seems to be because we use a lot of nested resources. It looks like the resource names are struggling to display when the resources are nested within a deployment resource. Is this a bug or am I using the extension incorrectly?
When the resource is nested:

When I move the resource to the root it's fine (but no longer linked to the parent):

Again, apologies if this is just me misunderstanding, but as far as I can see the names should resolve correctly?

To Reproduce

 {
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "asbResourceGroup": {
      "type": "string"
    }
  },
  "variables": {
    "topic-name": "my.topic"
  },
  "resources": [
    {
      "apiVersion": "2018-05-01",
      "name": "eunEntities",
      "type": "Microsoft.Resources/deployments",
      "resourceGroup": "[parameters('asbResourceGroup')]",
      "properties": {
        "mode": "Incremental",
        "template": {
          "$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
          "contentVersion": "1.0.0.0",
          "parameters": {},
          "resources": [
            {
              "type": "Microsoft.ServiceBus/namespaces/topics",
              "name": "[concat(variables('topic-name'))]",
              "apiVersion": "2018-05-01"
            }
          ]
        }
      }
    }
  ]
}