Pet Food for Life Stages

The recent article "Live Long, Live Strong." was very interesting. For the most part, it was presented as established fact. However, I wonder how much research actually supports the concept of different foods for different life stages. If we look at the ancestors/cousins of our dogs and cats, once weaned, foxes and bobcats and coyotes and cheetahs eat pretty much the same food all their lives. What's so different about domestic carnivores?

The article gave many more specifics about dogs, while the recommendation of senior food for cats--who tend to lose weight with age--may be totally inappropriate.

And aren't there still only 2 recognized life stages (adult and growth/reproduction)? Don't all foods have to fit one category or the other to comply with AAFCO's model standards? How much different are all these life stage foods? Comparing ingredients, there doesn't seem to be a consistent pattern.

Are there any published studies showing the benefits of "life stage" foods--or is the research proprietary--or is the whole kit-and-kaboodle just marketing?