For science I took a kitchen knife to a Surface Pro 3 and the underside of my FW16.
Surface off-center:
Surface at 90 degrees:
Framework 16 off-center (top three scratches are the new ones, others are from rubbing in a backpack):
Framework at 90 degrees:
Takeaway - doesn’t seem too different, but Surface Pro’s scratches look lighter when viewed at 90-degree angle.
Edit: just out of curiosity tried the same pressure on the aluminum touchpad spacer. It left a scratch which is only visible slightly at 45-60 angle, otherwise totally not noticeable.