@apollo/client local-only field is not resolved when working with service worker

I have problems getting local-only fields via typePolicies to work in my app. My setup is the following:

This is one of my queries:

export const GET_ALL_DEBT_TOKENS = gql`
  query GetDebtTokens {
    getDebtTokens {
      totalSupplyUSD
      totalReserve
      totalReserve24hAgo

      token {
        address
        symbol
        priceUSD @client
        priceUSD24hAgo
      }
    }
  }
`;

And this is the config to resolve my local field:

export function CustomApolloProvider({ children }: PropsWithChildren<{}>) {
  const client = new ApolloClient({
    // TODO: replace with your own graphql server
    uri: 'https://flyby-router-demo.herokuapp.com/',

    cache: new InMemoryCache({
      typePolicies: {
        Token: {
          fields: {
            priceUSD: {
              read() {
                console.log('priceUSD read function is called');
                return 100;
              },
            },
          },
        },
      },
    }),
  });

  return <ApolloProvider client={client}>{children}</ApolloProvider>;
}

This is the relevant schema:

type Token {
  address: String! # contract address, used as id
  symbol: String!
  createdAt: String!
  #
  priceUSD24hAgo: Float!
  #
  isPoolToken: Boolean!
}

type DebtTokenMeta {
  token: Token!
  # borrower specific
  walletAmount: Float
  troveMintedAmount: Float
  stabilityLostAmount: Float
  stabilityCompoundAmount: Float

  # global
  stabilityDepositAPY: Float!
  totalDepositedStability: Float!
  totalReserve: Float!
  totalReserve24hAgo: Float!
  totalSupplyUSD: Float!
  totalSupplyUSD24hAgo: Float!
}

My dev server returns everything except the "priceUSD" field. I also never see that log in the console. I am wondering how I can mess up this simple get-started guide.
The field marked with "@client" is not in the query to my Mock Service Worker. I wonder if it is the mock service worker that is causing the issue or a simple mistake by me.