Pasting from Google Docs removes Bold style in TinyMCE

Question

I'm using TinyMCE and I noticed that when I copy/paste from Google Docs all the bolds disappear to become normal text.

Reproduction online: https://jsfiddle.net/qg4x6ctL/2/

My options:

tinymce.init({
  selector: '#content',
  placeholder: "Paste here",
  contextmenu: 'paste',
  plugins: [
    'link',
    'lists',
  ],
  convert_fonts_to_spans: false,
});