Я не понимаю в чём спор. С т.з. археологии, истории, лингвистики, Махаянские сутры более поздние и написанные на более позднем Санскрите. Причём первые сутры, как я читал, ещё идейно не отличались от ПК. Можно проследить тенденции развития мыслей в самой Махаяне.
The earliest textual evidence of "Mahāyāna" comes from sūtras originating around the beginning of the common era. Jan Nattier has noted that in some of the earliest Mahāyāna texts such as the Ugraparipṛccha Sūtra use the term "Mahāyāna", yet there is no doctrinal difference between Mahāyāna in this context and the early schools, and that "Mahāyāna" referred rather to the rigorous emulation of Gautama Buddha in the path of a bodhisattva seeking to become a fully enlightened buddha.[7] wiki