I opened a USB-C Expansion Card to look at the circuitry inside it (picture, for those curious).
I also wanted to take apart the USB-A card, and I noticed that the USB-A cards have a metal sliding cover / back plate, unlike the USB-C cards, which have a plastic one.
Unlike the USB-C Expansion Card, I wasn’t able to open the USB-A cards (following this guide).
That got me thinking about why it could be metal. The first thing that came to mind was that it had to be conductive and that some wire on the inside is soldered to it, and that could also have been the reason that I couldn’t get it open. However, nothing conductive in the Framework Laptop seems to make definite contact with the metal plate. The metal plate does make some contact with the outer metal housing, and the outer metal housing might make contact with the metal body of the laptop, but the contact isn’t amazing so I highly doubt it’s designed for this.
Does anyone have a clue?