Would you exclude Vajrayana from Mahayana? Shingon was removed from the Tibetan area years ago because they are two different systems with different history, and it was suggested by some Shingon followers who found the unending comparisons and such with Tibetan Vajrayana tiresome (IIRC). Tibetan and East Asian exist separately because they are distinct historical developments of Mahayana with several significant differences between the two, while the two groups share a lot within their own area. If anyone wants to discuss this topic about the differences between major Mahayana groups please open a topic for it in the Mahayana forum.
"While teachers of the middle way, mind only, transcendent wisdom, mantra, and other schools may have their own assertions, the fulfillment of those intentions is the same. There is not a single thing that is not contained within mind."
(Gampopa to Düsum Khyenpa, in "The First Karmapa", KTD Pub, p254)
“If you recognize the world of appearance and existence as the mind, realize the mind itself as empty, and have no grasping at the superiority of your realizations — this is the ultimate view."
(Chegom Dzongpa, in "The Book of Kadam", Wisdom Pub, p609)