That is how I read it.
And I've done that plenty of times myself. At least on young chickens, each rib has a sort-of joint in the middle of it. If I push on the sides of the chicken with my fingers, the ribs will bow in at a certain point (a spot on each rib, all lined up with each other.)...
You must be using "inedible" differently than I would. A tough chicken can be difficult to eat, but it certainly CAN be eaten (chop the meat small with a knife, or plan on lots of chewing.)
I do agree that less-tough chicken is preferable.