That was because of the difference in its words and terms...

That was because of the difference in its words and terms, and I am quite sure that all the confusion and inconsonance afflicting this hadith being done by the narrators. Also, al-Suyuti, after citing the statements of the ulama’ in regard of these ambiguous traditions, expressed an odd opinion I cite herewith for the sake of jesting with readers.

"Hence among the twelve successors, we can mention the four caliphs (Rightly-guided), with al-Hasan, Mu'awiyah, Ibn al-Zubayr and Umar ibn Abd al-Aziz, who altogether constitute eight caliphs. Then it can be added to them al-Mahdi from the Abbasids as his position among them is the same as that of Umar ibn Abd al-Aziz among the Umayyads, beside al-Zahir due to his being characterized with justice. After that remain the two awaited (caliphs)!! one of whom being al-Mahdi!

as he belongs to the household of Muhammad (S)". But he missed to mention the second awaited one…and may God’s mercy be upon that who said in regard of al-Suyuti that: he was a night wood-cutter. 445 Before concluding our speech about al-Mahdi, I cite herewith a statement about him uttered by al-Allamah Murtada al-Askari, one of the Iraqi eminent great ulama’, that revealing the belief held by the Ithna Ashari Imami Shi'ah toward al-Mahdi.

In a long reply (to a question) he sent to us, he said: The Ithna-Ashari Shi'ah hold that the earth was never devoid of an authority for Allah upon His creation, and will never be devoid too. And he either be alive as a prophet to whom it is revealed, or anyone appointed by him to take charge of his Shari`ah after him, and clarify it for his Ummah.

"They consider the traditions you cited in your book pp.210-211, 446 under the heading "al-Khulafa' al-Ithna-Ashar" (the Twelve Caliphs), as an indication of the Twelve Imams taking charge of the Din after the Prophet, as this number applies neither to the Rashidun, nor the Umayyad caliphs, nor others. Besides, they narrate hundreds of traditions, through their special turuq (chains of transmission) from the Messenger of Allah, that indisputably determine this fact.

Also they believe that the Twelfth of these Imams being al-Mahdi, the son of al-Hasan al-Askari, who was born in Samarra' in 255 H., whom they believe to be still alive, as in the case of Noah who lived among his folk for a thousand years save fifty years, and that of Jesus whom they slew not nor crucified but it appeared so unto them, but Allah took him up unto Himself.