This Ember belongsTo relationship is working, but I can't see how

I've been developing an app for about a year now, so I started it mid-2014 and have been upgrading ember.js and ember-cli as things move forward on those projects. I'm at Ember 1.11 now.

My JSON API returns a main projects object, along with other sideloaded objects (like projectStatus). What I can't understand is, since I don't have any adapters or serializers that specify this, how I'm it's able to use the returned JSON, because it looks like this:

{
  "projects" : {
    "id": 4462875
    "projectName" : "New business from Acme",
    "projectDescription" : "Just another great project",
    "pmlinks" : [ 1, 2],
    "statusLinks" : [ 1440 ],
    "commentsLinks" : [ 39 ]
  },
  "projectResources" : [ {
    "id" : 1,
    "name" : "Wile E. Coyote"
  }, {
    "id" : 2,
    "name" : "Roadrunner"
  }],
  "projectComments" : [ {
    "id" : 39,
    "projectComment" : "started the project",
  } ],
  "projectStatuses" : [ {
    "id" : 1440,
    "status" : "G",
    "trending" : "N",
    "comment" : null,
    "lastModifiedDate" : "2015-07-17T13:46:11.037+0000",
    "project" : 4462875
  } ],
}

I can't find anything in the Ember docs that reccomend this "*Links" format for the relationships, and in fact it suggests using something more like status_ids. But the example it shows doesn't use _ids so I'm even more confused.

Here's a snippet of my project model:

statusUpdates: DS.hasMany('projectStatus'),
projectComments: DS.hasMany('projectComment'),
projectResources: DS.hasMany('projectResource'),

What I'm trying to figure out is with my new belongsTo relationship to schedule, how should the JSON be formatted from the API? It seems to work if the project object has a property like this "scheduleLinks": [10] but not if it's like "schedule": 10 or "schedule_id": 10 and that seems to be what the documentation says should work.