I would stick with the large breed puppy until 12 months.
My reasoning is that since Blue Buffalo only show their minimum calcium and phosphorous levels and not their maximums, their large breed puppy formula is the only one "advertised" to meet proper bone development for large breed puppies on the bag.
I would suspect that they are internally stricter about this on the large breed puppy formula on every batch without disclosing their maximum calcium and phosphorous levels to the public.
I don't like that they hide this, but I'm sure that they are not in business to harm dogs either, so I'd stick to their recommendation and feeding guidelines to not risk it.
Once your puppy is an adult, even the regular adult formula has large breed feeding guidelines; therefore, their large breed adult bag just has extra glucosamine and l-carnitine that's not really needed.