"Nichiren Shoshu Priests have studied the Gosho in depth--in its original language. Their formal training lasts for years." -- Nichiren Shoshu member
Nichiren Daishonin never studied the texts of the Buddha in Sanskrit or Pali. Does that mean his enlightenment was inferior to Bhikshu Bodhi's? The Daimoku contains all the merits and virtues of the Eternal Buddha. When we chant Namu Myoho renge kyo with strong and correct faith, we enjoy the very same enlightenment as He.
Besides, the Nichiren Shoshu priests study predominantly the modern Japanese Gosho Zenshu, not Nichiren's works in Medieval Japanese and Chinese.