As @PensiveShadow said, cornrows are tighter making them a protective style for coily and textured hair. To take them out, you have to start from the bottom. For dutch braids, you can pull out the strands of hair more easily because dutch braids are done on straighter hair.
The origins are different:
Only thing this screenshot got wrong is that the dutch/french braid mention in the 1871 story never actually referred to cornrows and also never provided a visual of what they looked like, so we can assume the author was talking about a different hairstyle