Subscription Previous Values for Linked Records

I’ve got a subscription that is watching a linked record field to see if new records have been linked. It’s working, but it’s not showing the previous list of linked records in the “Previous Values” object. This subscription will trigger user notifications, so we need to basically suppress sending notifications to all of the previously linked records so we’re not spamming everyone. Maybe there’s a better way to do this so let me know. Thanks!

Here’s the subscription

subscription {
  Projects(filter: {
    mutation_in: [update],
    updatedFields: {
      contains: ["assignedWorkers"]
    }
  })  {
    node {
     	id
      name
      org {
        id
        name
      }
      assignedWorkers {
        items {
          id
          user {
            id
            email
            firstName
            lastName
          }
        }
      }
    }
    previousValues {
      assignedWorkers {
        items {
          id
          user {
            id
            email
            firstName
            lastName
          	}
          }
        }
      }
    mutation
  }
}