The Pure Lands preached in the pre-Lotus expedient sūtras are mere substitutes tentatively shown by replicas of Śākyamuni Buddha, the Eternal True Buddha. In fact, they all are lands of impurity. Therefore, when the true Pure Land was decided in “The Life Span of the Buddha” chapter of the Lotus Sūtra, the essence of which consists of chapters on the “Expedients” and “The Life Span of the Buddha,” it was declared that this Sahā World is the true Pure Land of the Tranquil Light.
As for the question why, the Lotus Sūtra also recommends the Tuṣita Heaven, the Realm of Peace and Sustenance (Pure Land of the Buddha of Infinite Life), and Pure Lands all over the universe, it is merely that designations of the Pure Lands, such as Tuṣita Heaven and Realm of Peace and Sustenance, preached in the pre-Lotus sūtras are used without modification to name the Pure Lands to be established in this world. It is like names of the three vehicles (śrāvaka, pratyekabuddha, and bodhisattva) mentioned in the Lotus Sūtra, which does not actually preach three different teachings; it preaches the sole teaching leading to Buddhahood. It is stated in the Lotus Sūtra, chapter 23, that those who practice this sūtra “will immediately be reborn in the World of Happiness.” In the Annotations on the Words and Phrases of the Lotus Sūtra, fascicle 10, Grand Master Miao-lê interprets: “This does not mean the Pure Land of the Buddha of Infinite Life preached in the Sūtra of Meditation on the Buddha of Infinite Life.” His interpretation is the same as stated above.
People today without karmic relations with the Lotus Sūtra, wishing to be reborn in the Pure Land to the west, are in fact praying for rebirth in the land of rubble, giving up the Sahā World, which is the true Pure Land. People who do not believe in the Lotus Sūtra will not be able to be reborn even in such lands as Tuṣita Heaven and Realm of Peace and Sustenance, which are in reality the Pure Lands in this Sahā World given such temporary names.
Shugo Kokka-ron, Treatise on Protecting the Nation, Writings of Nichiren Shōnin, Doctrine 1, Pages 68-69