prototype pollution

adapters.my-model\.js

import RESTAdapter from 'ember-data/adapters/rest';

export default class extends RESTAdapter {
  ajax(path, method, options) {    
    return {
      myModels: [{
        id: 1,
        name: 'Model 1'
      }]
    };
  }	 
}

controllers.application\.js

import Controller from '@ember/controller';

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';
}

models.my-model\.js

import Model from 'ember-data/model';
/*
import attr from 'ember-data/attr';
import { belongsTo, hasMany } from 'ember-data/relationships';
*/

export default class extends Model {
}

routes.application\.js

import Route from '@ember/routing/route';
import { inject } from '@ember/service';
import { A as emberA } from '@ember/array';

export default class extends Route {
  @inject store;
  
  model() {
    return this.store.findAll('my-model');
  }
  
  setupController(controller, model) {
    const recordArray = model;
    const emberArray = emberA();
    const nativeArray = [];
    
    console.log('the arrays...');
    console.log('record array', recordArray);
    console.log('ember array', emberArray);
    console.log('native array', nativeArray);
    
    console.log('');
    console.log('do they have kvo methods?...');
    console.log('record array', !!recordArray.pushObject);
    console.log('ember array', !!emberArray.pushObject);
    console.log('native array', !!nativeArray.pushObject);
    
    console.log('');
    console.log('do they have kvo methods after slicing?');
    console.log('record array', !!recordArray.slice().pushObject);
    console.log('^ one would expect this to be false');
    
  }
} 

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "EXTEND_PROTOTYPES": false,
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0",
    "ember-data": "3.18.0"
  }
}