With the Intel MBs having identical ports, it likely wasn’t even a consideration, but with the AMD boards on both the 13 and 16 having different ports, Framework introduced port maps showing each port’s capabilities.
While they’re relatively simple to follow, if the port numbers could be etched/milled/cast into the chassis, it would remove the initial “does this card work in this port?” uncertainty on AMD systems, and may reduce support requests. Specifically, I know when I was setting up my 16 for the first time, I had the laptop flipped over and reversed (bottoms up and dGPU forward) compared to the port map available online.