Just a quick question.

Adolescent dogs don't poop more at night, but several times throughout a 24 hour period because their small systems are not on any kind of regular maintenance programme. Until their systems develop they will continue to poop that way. Don't forget, dogs mature faster, are still in puppy hood at their 2 year mark when they are more less teenages.

Tick

Resting, like they do at night when with the mother aids digestion. During the day they are eating less and actively running around and exploring. They can eat but hold the food in their stomach until they get a quiet time to digest it. Excitement and strenuous activity slow digetion, resting encourages it. You know how mom always said wait an hour after you eat before going swimming?

Also when puppies are laying down there is more pressure on their bladders and bowels. Any little morsel of food will put pressure on them. But like Tick mentioned, it's necessarily more frequent at night, it's more of a consistent process during the run of 24 hours.

On top of everything else said.. Please keep in mind that you are training the muscles in the body, such as the bladder muscle, to become stronger and hold it for 8 hours or so.