Противоречие относительно количества допустимых жен в никах аль-мута?

Ассаляму алейкум. У меня вопрос к Вам: на одном из англоязычных сайтов, специализирующихся на борьбе с шиизмом, я нашел следующее:

In Al-Istibsar (p. 693), Al-Tusi narrates from Mohammad bin Ya’qoub from Al-Hussain bin Mohammad from Ahmad bin Is’haaq Al-Ash’ari from Bakr bin Mohammad Al-Azdi that he said:
I asked Al-Redha – peace be upon him – about mutah, and if it is included within the (limit of) four. He said: No.
Al-Majlisi grades this hadith as authentic in Malath Al-Akhyar.
In Al-Kafi 5/1084 we find a similar narration from Ali bin Ibrahim from his father from Ibn Abi Umair from Omar bin Uthaina from Abi Abdullah – peace be upon him – that he was asked how many mutah (wives) can one have? He said: They are like slave girls.
However, in Al-Istibsar (p. 693), from the path of Ibn Abi Nasr that he asked Al-Redha:
I asked him about a man that is married to a woman and if it is possible to marry her sister as mutah. He said: No. I said: Zurarah narrates from Abi Ja’afar – peace be upon him – that they (mutah wives) are like slave girls and one can marry as much as one likes. He said: No, they are from the four.
Al-Tusi also narrates from Mohammad bin Hasan Al-Saffar from Mu’awiyah bin Hakeem from Ali bin Al-Hasan bin Ribat from Abdullah bin Muskan from Ammar Al-Sabati from Abi Abdullah (that he was asked) about mutah, so he said: They are from the four.
Al-Majlisi grades these two narrations as authentic as well.

So, we ask Shias:
How is it possible for the infallible Imams to legislate that one can marry an unlimited number of mutah women, then state that they are one of the four?

Шейх, не могли бы Вы прояснить данный момент? Простите, что не стал переводить, однако, насколько я знаю, Вы владеете английским.