PrestaShop 1.6 uses a bit different method to generate tinyMCE rich text editor than older releases of PS engine. The most important thing now is fact, that editor is executed from one file, not from many different files as it was before. This is definitely an advantage of new engine, because you can easily extend editor globally, for whole shop. It just mean that one file decides how the textbox tinyMCE editor looks like for product description, short description, category descriptions, cms page editor etc.