From what I've heard, the newer Pampers and Huggies are made with newer, more advanced machines that can make more "hourglass shaped" diapers and have things like "3 channel absorption."
For an ABDL manufacturer like ABU or Bambino, they'd have to spend a LOT of money to build or borrow one of these machines. Since there's a large barrier of entry and P&G and Kimberly-Clark have deep pockets/higher demand for their products, they will have easier access to these machines where they can create these fancy baby diapers.