Hello and welcome to the forum. The name for this is coprophagia and as tinyplanets says, it is not uncommon. Why some dogs do it and other dogs don’t is something of a mystery but as your pup is young it could be that his breeder was not quick enough to clean up or perhaps he needed more food. That’s conjecture though.
Anyway, he has started the habit and unfortunately it is one which is not easy to solve. Some folk say pineapple helps, others recommend putting chilli powder on the poo. In my experience they don’t work. The only thing that does work is vigilance and cleaning up immediately.
You need to encourage him to poo when you are there. If he is not supervised then use a light muzzle.
Diet wise, I am not familiar with the foods that you are using but having just checked, Autarky Puppy review is here
and the nutritional rating is 75% so it is not bad. Most dry foods have a high carb content (part of which is fibre), needed to form the biscuit. Because of this dogs usually have bigger stools when on dry food. If they have not been able to process all of this, maybe there is residue that is attractive to them. Dogs that are fed fresh cooked or raw food have much smaller, firm stools because there are no so called ‘fillers’. Arguably, this type of stool is a perhaps less attractive as there would be no, or little sugar content.
There are other threads on this topic so if you want to look at them use the search box and the term ‘coprophagia’.