testing scroll position on iOS in karma on SauceLabs?

I am working on the unit tests for react-selection-hoc and have hit a stumbling block: iOS refuses to cooperate on SauceLabs for the most basic test:

it("should return the correct page offset", () => {
  if (window.____isjsdom) return
  class Boohoo extends React.Component {
    render() {
      return (
        <div style=>
          <div style=>one</div>
          <div style=>two</div>
          <div style=>three</div>
          <div style=>four</div>
        </div>
      )
    }
  }

  var div = document.createElement('div');
  document.body.appendChild(div)
  var component = render(<Boohoo />, div);
  window.scroll(20,20)
  expect(document.body.scrollTop).to.equal(20)

  const a = mouseMath.pageOffset('left')
  const b = mouseMath.pageOffset('top')

  expect(b).to.equal(20, "top should be 20")
  expect(a).to.equal(20, "left should be 20")
  unmountComponentAtNode(div)
})

})

The code it is testing is here:

  static pageOffset(dir, win = window) {
    if (dir !== 'left' && dir !== 'top') {
      throw new Error(`direction must be one of top or left, was "${dir}"`)
    }
    let actual = win
    if (win.parent) {
      actual = win.parent.window
    }
    let offset = dir === 'left' ? 'pageXOffset' : 'pageYOffset'
    offset = actual[offset] ? actual[offset] : 0
    return offset || 0
  }

which injects window as a dependency for testing the logic of the method. I am using SauceLabs in order to test the actual code on every browser to make sure the concept is valid. The thing is, the concept is valid: a manual test inside a browserstack real iPhone using DevTools to scroll by 20 shows that window.parent.window.scrollY is set to 20. Yet, doing this inside SauceLabs fails. I can see the thing running inside a simulated iPhone with the realtime video feature, and it looks normal, yet fails every single time.

What do I need to do to configure SauceLabs so the dang thing actually renders correctly to mirror how reality works?