Zhiyi, I believe, awakened to the same truth that the creators of the Lotus Sūtra did. He expressed it in terms of the “three thousand realms in a single thought-moment.” However, the full import of what the creators of the Lotus Sūtra and Zhiyi realized will not be revealed until we discuss the Original Gate and the Buddha’s attainment of buddhahood in the remotest past. The One Vehicle teaching was only the relatively shallow beginning of what they realized. As Nichiren says a little further on in Kaimoku-shō:

The second chapter, “Expedients,” in the Trace Gate of the Lotus Sūtra makes up for one of the two faults of the pre-Lotus sūtras by revealing the teachings of the three thousand realms in a single thought-moment’ and ‘attainment of buddhahood by the people of the two vehicles.’ Yet, since the chapter has not yet revealed the Original and Eternal Buddha by ‘outgrowing the provisional and revealing the essential,’ it does not show the real concept of the ‘three thousand realms in a single thought-moment.’ Nor does it establish the true meaning of ‘attainment of buddhahood by people of the two vehicles.’ They are like the reflections of the moon in the water, or rootless grass floating on waves. (Hori 2002, p. 48)