Resolving keypaths (or chained relationships) in route

I am processing a bunch of records and producing an array of hashes for a third party library. For the life of me I can't figure out why this doesn't work.

export default Route.extend({
  model: function(params) {
   let qp = {viewName: 'byDay'};

  return this.store.query('job-receipt', qp).then(
   (receipts)=>
    all(
      retval.map(
        (receipt)=>
          hash({
            stockCode: receipt.get('job')
                                   .then(job => job.get('stockCode'))
                                   .then(stockCode => stockCode.get('stockCode')),
            productClass: receipt.get('job')
                                  .then(job => job.get('stockCode'))
                                  .then(stockCode => stockCode.get('productClass'))
                                  .then(productClass => productClass.get('descr')),
            qtyRecvd: receipt.get('qtyRecvd')
          })
        )
      )
);

If I keep reentering the route, eventually the promises resolve. If I check, the productClass promise just straight up gets called with a null value. Why isn't it waiting for the stockCode.get('productClass') to resolve? I know there are real values in there because it does eventually resolve.

I'm missing something super basic. I've tried Ember.get(thing, keypath) etc. Don't these all return promises? Isn't the RSVP.hash supposed to wait for all the promises to resolve before proceeding? Like I said, I know the data is good because eventually it does resolve (as opposed to me just not handling a rejection).

Thanks in advance, John