The impression I've always had is that ribbon cables and flexible pcb don't really fit in to any of the board categories. Is that 100% the case all the time or are there exceptions? If there are exceptions what do I need to look for?

Here are some different examples. Some with ICs, gold pin connectors, regular ribbon cable with flat gold connectors.

_________________
Here to learn more so I can recycle more
My grades are my own opinion and not an official grade from Boardsort

someone took apart a laptop or professional tablet.

The connectors are all Cable ends
The occupied plastic board sections are high peripheral
The clean bare wire goes with mixed wire

if that one Gold finger connector is rigid, it will go with Gold fingers if it is thin and flexible it goes with Cable ends

_________________
42 6F 61 72 64 73 6F 72 74 2E 63 6F 6D