Pet diets has more nonsense and assumptions written about it from owners who transfer their personal experiences to an assumtpion that it's right for everyone than many other subjects.
There are some, few, breed and dog size specific issues one sould allow for.. that small breed dogs are generally more prone to dental issues than the larger breeds such that the texture of food can be manipulated to assist. A claasic bred like the Dalmatian has a predisposition to protein 'allergies' (look up dalmatian bronzing syndrome if interested) and a subset with difficulties convering uric acid to urea. Other breeds may have statistical tendencies to their own issues but this is usually manifest because people pick one convenient bag of food and that highlights the problem.
Any half-decent manufacturer of dog food follows the bell-curve of minimum dietary requirements but sometimes they fail to monitor excesses. Premium (so called life stage) diets come from manufactureres that manipulate the bell curves of those diet rquirements to help specific syndromes but still stay within that curve.
Variation is probably the key to avoding intolerances and for most folk reducing the excesses they feed their dogs would probably be beneficial. However reducing the bulk of stool is probably a bad idea and Id guess I solved more digestive problems by recommending bulking agents than the other way around.
I used to suggest that owners without a peanut allergy might try eating a handful of roast monkey nuts.. shells and all.. and assess the benefits for themselves- the ideal being a big product that floats in the pan! And for their dogs often the answer was to shell the peanuts and grind the shels up into the dog's food as a solution for anal sac problems, colitis and the like.
When it comes to texture I used to suggest to folk they eat some biscuits– ginger nuts fr example- and then look at their own teeth. many biscuits just stick and dogs aren't so cooperative to brushing. Specifically marketed teeth cleaning things often come up short of working. The only really relaible one I came across is Hills T/D and my own dog gets some of that (overpriced) stuff daily to solve the problem of recurrent dental scaling. Bones and raw food also work but obvious hazards and my own hound just gets distressed rushign around the farm buryng and digging up the bone to re-hide it. And ends up with a raw bleeding nose.