Some sutras are not recognized by sectarian Buddhists as authoritative because they are not included in their own scriptural collections. But are only their own sutras authoritative? Or should what the Buddha taught be the authority? If they only accept their own scriptural canons, then the Buddha is not their Teacher and they are not His disciples*.
It is unreasonable to claim that our teachings are not the words of the Buddha simply because they are not included in their own collection of sutras, since they are found in other canons and do not contradict other discourses or the truth of the Dharma.
It is overly bold of them to claim that our scriptures are not what the Buddha taught simply because they chose not to include them in their own canon of scripture.
—Vasubandhu, in Refutation of the Theory of a Self 2.6.1*If they determine which teachings of the Buddha they accept, and which they do not, then they are, in fact, their own teachers.