I have the ER4PT on hand myself. And I have to say that I hear the difference between with and without the S adapter more along the lines of how the HeadRoom plots portray it. S adapter gives more clarity, more "air", more accurate all around. At the cost of that little 8k peak adding a bit of glare. But it definitely makes the ER4PT seem mid-fi in comparison.
Rest easy luis, your ER4S is still better than the PT configuration. At least by what I interpret to be your standards.