Defining an index on an abstract type doesn't work correctly

For example, if you apply this diff to the EG test schema and config:

diff --git a/config/schema/widgets.rb b/config/schema/widgets.rb
index 7df5223f..f24e9da1 100644
--- a/config/schema/widgets.rb
+++ b/config/schema/widgets.rb
@@ -296,36 +296,28 @@ ElasticGraph.define_schema do |schema|
 
   schema.object_type "MechanicalPart" do |t|
     t.root_query_fields plural: "mechanical_parts"
-    t.implements "NamedEntity"
     t.field "id", "ID!"
     t.field "name", "String"
     t.field "created_at", "DateTime!"
     t.field "material", "Material"
     t.relates_to_many "components", "Component", via: "part_ids", dir: :in, singular: "component"
     t.relates_to_one "manufacturer", "Manufacturer", via: "manufacturer_id", dir: :out
-
-    t.index "mechanical_parts" do |i|
-      i.default_sort "created_at", :desc
-    end
   end
 
   schema.object_type "ElectricalPart" do |t|
     t.root_query_fields plural: "electrical_parts"
-    t.implements "NamedEntity"
     t.field "id", "ID!"
     t.field "name", "String"
     t.field "created_at", "DateTime!"
     t.field "voltage", "Int!"
     t.relates_to_many "components", "Component", via: "part_ids", dir: :in, singular: "component"
     t.relates_to_one "manufacturer", "Manufacturer", via: "manufacturer_id", dir: :out
-
-    t.index "electrical_parts" do |i|
-      i.default_sort "created_at", :desc
-    end
   end
 
   schema.union_type "Part" do |t|
     t.subtypes "MechanicalPart", "ElectricalPart"
+
+    t.index "parts"
   end
 
   # Note: `Manufacturer` is used in our tests as an example of an indexed type that has no list fields, so we should
diff --git a/config/settings/development.yaml b/config/settings/development.yaml
index cbc914cd..631a9233 100644
--- a/config/settings/development.yaml
+++ b/config/settings/development.yaml
@@ -17,9 +17,8 @@ datastore:
         number_of_shards: 1
       setting_overrides_by_timestamp: {}
     components: *main_index_settings
-    electrical_parts: *main_index_settings
     manufacturers: *main_index_settings
-    mechanical_parts: *main_index_settings
+    parts: *main_index_settings
     teams: *main_index_settings
     widget_currencies: *main_index_settings
     widgets: *main_index_settings

...and then run bundle exec rake boot_locally, you get failures:

1) ElectricalPart:vzednoadoitbhjhwvbyb@v11: Malformed event payload. Validation errors:

{
  "data_pointer": "/type",
  "schema_pointer": "/$defs/ElasticGraphEventEnvelope/properties/type",
  "type": "enum",
  "error": "value at `/type` is not one of: [\"Address\", \"Component\", \"Manufacturer\", \"Sponsor\", \"Team\", \"Widget\", \"WidgetWorkspace\"]"
}

The problem is the affect it has on the JSON schema:

diff --git a/config/schema/artifacts/json_schemas.yaml b/config/schema/artifacts/json_schemas.yaml
index 8e37c372..b3ca929a 100644
--- a/config/schema/artifacts/json_schemas.yaml
+++ b/config/schema/artifacts/json_schemas.yaml
@@ -24,9 +24,7 @@ json_schema_version: 1
         enum:
         - Address
         - Component
-        - ElectricalPart
         - Manufacturer
-        - MechanicalPart
         - Sponsor
         - Team
         - Widget
@@ -243,39 +241,6 @@ json_schema_version: 1
   DateTime:
     type: string
     format: date-time
-  ElectricalPart:
-    type: object
-    properties:
-      id:
-        allOf:
-        - "$ref": "#/$defs/ID"
-        - maxLength: 8191
-      name:
-        anyOf:
-        - allOf:
-          - "$ref": "#/$defs/String"
-          - maxLength: 8191
-        - type: 'null'
-      created_at:
-        "$ref": "#/$defs/DateTime"
-      voltage:
-        "$ref": "#/$defs/Int"
-      manufacturer_id:
-        anyOf:
-        - allOf:
-          - "$ref": "#/$defs/ID"
-          - maxLength: 8191
-        - type: 'null'
-      __typename:
-        type: string
-        const: ElectricalPart
-        default: ElectricalPart
-    required:
-    - id
-    - name
-    - created_at
-    - voltage
-    - manufacturer_id
   Float:
     type: number
   GeoLocation:
@@ -369,46 +334,6 @@ json_schema_version: 1
     - id
     - name
     - created_at
-  Material:
-    type: string
-    enum:
-    - ALLOY
-    - CARBON_FIBER
-  MechanicalPart:
-    type: object
-    properties:
-      id:
-        allOf:
-        - "$ref": "#/$defs/ID"
-        - maxLength: 8191
-      name:
-        anyOf:
-        - allOf:
-          - "$ref": "#/$defs/String"
-          - maxLength: 8191
-        - type: 'null'
-      created_at:
-        "$ref": "#/$defs/DateTime"
-      material:
-        anyOf:
-        - "$ref": "#/$defs/Material"
-        - type: 'null'
-      manufacturer_id:
-        anyOf:
-        - allOf:
-          - "$ref": "#/$defs/ID"
-          - maxLength: 8191
-        - type: 'null'
-      __typename:
-        type: string
-        const: MechanicalPart
-        default: MechanicalPart
-    required:
-    - id
-    - name
-    - created_at
-    - material
-    - manufacturer_id
   Money:
     type: object
     properties:

The JSON schemas for these types should be retained, even though there is no longer an index definition directly on them. They are still a root type within an index.