And the explanation of this evidence that tayammum is not like ghusl in all legal rulings, because a person who performs ghusl due to janabah will only be required to perform ghusl again when he becomes junub again. Whereas a person who performs tayammum due to janabah in the absence of water will be required to perform ghusl when water becomes available.

Sayyiduna Imran bin Husain (may Allah be pleased with him) narrates that we were on a journey with the Messenger of Allah (peace and blessings be upon him), and we traveled through the night until, when it was the time of sahar before dawn, we camped. There is no moment more delightful for a traveler than the sleep of the last part of the night (so we slept). The heat of the sun was what woke us up (meaning, we slept late into the morning and missed the Fajr prayer). Then he narrated part of the hadith and said: Then the Prophet (peace and blessings be upon him) had the call to prayer given for the prayer and led the people in prayer. When he finished the prayer, suddenly he noticed a man sitting apart who had not prayed with the people. The Prophet (peace and blessings be upon him) asked him:“O so-and-so, what prevented you from praying with the people?”He replied,“O Messenger of Allah, I became junub (in a state of major ritual impurity) and there is no water.”The Prophet (peace and blessings be upon him) said:“It is obligatory upon you to perform tayammum with clean earth, for that will suffice you.”Then the Prophet (peace and blessings be upon him) set out, and along the way, the people complained to him about the scarcity of water. So the Prophet (peace and blessings be upon him) called for so-and-so (Abu Raja mentioned his name but ‘Awf forgot it) and called for Sayyiduna Ali (may Allah be pleased with him), and ordered them:“Go and search for water for us.”So the two of them set out in search of water. They met a woman who was riding on her camel between two water skins or water bags. Then he narrated part of the hadith and said: Then the Prophet (peace and blessings be upon him) had it announced among the people:“Let the animals drink and you also drink.”So whoever wished, let his animals drink, and whoever wished, drank himself. Finally, the Prophet (peace and blessings be upon him) gave a water vessel to the man who had become junub and said:“Go and pour it over yourself (i.e., perform ghusl).”Imam Abu Bakr (may Allah have mercy on him) said: In this hadith, there is also evidence that a person who prays with tayammum, when he finds water, must perform ghusl if he was junub, and if he was in a state of minor impurity, he must perform wudu. But it is not obligatory for him to repeat the prayers he performed with tayammum, because the Prophet (peace and blessings be upon him), when he ordered the one who prayed with tayammum to perform ghusl upon finding water, did not order him to repeat the prayers he had performed with tayammum. In this hadith, there is also evidence that for the one performing ghusl for janabah, it is not obligatory to perform wudu before pouring water over the rest of the body, because when the Prophet (peace and blessings be upon him) ordered the junub man to pour water over his body, he did not order him to begin with wudu and washing the limbs of wudu and then pour water over the whole body. By the command of the Prophet (peace and blessings be upon him), it is clear and correct that when a junub person pours water over his body, he is considered to have performed the obligatory ghusl. And in this, there is also evidence that beginning with wudu and then pouring water over the whole body for the one performing ghusl is optional and recommended, not obligatory or compulsory.