Non-async relationship bug (working in 3.1.1)

adapters.application.js

import Adapter from "ember-data/adapters/json-api";

export default Adapter.extend();

initializers.pretender.js

export function returnJSON(status, body) {
  return json(...arguments);
};

export function json(status, body) {
  if (arguments.length === 1) {
    body = status;
    status = 200;
  }
  
  return [
    status,
    { "Content-Type": "application/json" },
    JSON.stringify(body)
  ];
};

export const server = new Pretender();

export function initialize() {
  server.handledRequest = function(verb, path, request) {
    console.log(`handled request to ${verb} ${path}`);
  }

  server.unhandledRequest = function(verb, path, request) {
    console.log(`undhandled request ${verb} ${path}`);
  }
};

export default {
  name: 'pretender',
  initialize
};

models.comment.js

import DS from 'ember-data';

export default DS.Model.extend({
  post: DS.belongsTo(),
  text: DS.attr('string')
});

models.post.js

import DS from 'ember-data';

export default DS.Model.extend({
  comments: DS.hasMany('comment', { async: false }),
  name: DS.attr('string')
});

routes.application.js

import Ember from 'ember';
import { server, json } from '../initializers/pretender';

server.map(function() {
  this.get('/posts/1', function() {
    return json({
      data: { 
        id: 1, 
        type: 'post',
        attributes: {
          name: "Mark Twain"
        },
        relationships: {
          comments: {
            data: [{
              id: 1,
              type: 'comment'
            }],
            links: {
              related: '/posts/1/comments'
            }
          }
        }
      }
    });
  });
  
  this.get('/posts/1/comments', function() {
    return json({
      data: [
        { 
          id: 1, 
          type: 'comment',
          attributes: {
            text: 'Bla'
          },
          relationships: {
            post: {
              data: {
                id: 1,
                type: 'post'
              }
            }
          }
        }
      ]
    });
  });
});

export default Ember.Route.extend({
  model() {
    return this.get('store').findRecord('post', 1);
  },
  afterModel(post) {
    return post.hasMany('comments').reload();
  }
});

serializers.application.js

import Serializer from "ember-data/serializers/json-api";

export default Serializer.extend();

templates.application.hbs

<h2>My Library</h2>
<hr>
{{model.name}}

{{#each model.comments as |comment| }}
  <p>Comment: {{comment.text}}</p>
{{/each}}

twiddle.json

{
  "version": "0.10.4",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "3.1.2",
    "ember-template-compiler": "3.2.2",
    "route-recognizer": "https://rawgit.com/tildeio/route-recognizer/56f5fcec6ae58d8e86b5dc77609809fb91198142/dist/route-recognizer.js",
    "FakeXMLHttpRequest": "https://rawgit.com/pretenderjs/FakeXMLHttpRequest/23c3a96b5b24f1bfe595867437e4f128a29c2840/fake_xml_http_request.js",
    "pretender": "https://rawgit.com/pretenderjs/pretender/c6de9afe18b1472aded2592f5a80ad9a26a0e262/pretender.js"
  },
  "addons": {
  	"ember-data": "3.1.1"
  }
}