In usb-a cables you can actually see the pins themselves missing looking into the connector from the outside; in usb-c not so much (or at least i could not really see anything there). I could never figure out how to determine a no-data usb-c cable, though I have only even seen one anyway.
The problem with stiffness etc is that there is already a lot of variability on usb-c cables, though there could definitely be something there that I just did not notice.
