Migrating entitiies in managed federation

We have a situation where we have set up managed gql federation. We want to move definitions and resolvers of some entities from one service to other.
It can be illustrated on the example of Entities - Federation - Apollo GraphQL Docs
Our service “gateway-service” defines entity “ExternalDraftDeal” with some extensions

type ExternalDraftDeal @key(fields: "id") {
  id: ID!
  acquisitionId: String
  createdAt: String!
  createdBy: Author!
}

extend type ExternalDraftDeal {
  author: AuthorDetails!
}

... #some other entities and types

# Not sure if this union is also important or not
union ExternalDealsUnion = ExternalDraftDeal | ExternalLockedDeal | ExternalPublishedDeal | ExternalUnlockedDeal | ExternalArchivedDeal

We want to move this entity to deals-service (only the base entity). This entity is defined there as

type ExternalDraftDeal @key(fields: "id") {
  id: ID!
  acquisitionId: String
  createdAt: String!
  createdBy: Author!
}

... #some other entities and types

# Not sure if this union is also important or not
union ExternalDealsUnion = ExternalDraftDeal | ExternalLockedDeal | ExternalPublishedDeal | ExternalUnlockedDeal | ExternalArchivedDeal

However when checking the types from the deals-service by executing

npx -p @apollo/rover rover subgraph check 

We get the following error

VALUE_TYPE_NO_ENTITY: [gateway-service] ExternalDraftDeal -> Value types cannot be entities (using the `@key` directive). Please ensure that the `ExternalDraftDeal` type is extended properly or remove the `@key` directive if this is not an entity.

According to the docs at Understanding errors - Apollo Server - Apollo GraphQL Docs this error indicates that we can’t have tow identical entities. However the migration tutorial explicitly states that for migration we should have identical entities.