This statement you are making is too general, so it is not an accurate representation of what Bahai's believe.
Baha'is believe there has been misinterpretations and misunderstandings with regards to Recorded Traditions and verses of Holy Books, and that Bahaullah provided correct understanding of them. Even with regards to Bible, Bahais believe overall it is the Truth, with just some minor inaccuracies which are not significant.
Specifically, Bahaullah appeared among a People whose Religious beliefs were mostly Abrahamic, and in particular Islam. Thus, in order for Him to guide those people, He had to use the Recorded Traditions in the Islamic sources as well as Biblical Traditions. According to history, Bahaullah wrote His works in form of Tablets and Books to respond to questions, and to teach people, the Religious Truth, and that many Witnesses have said that Bahaullah wrote His works in front of them, without using other books to quote from. This is despite the fact that, He frequently quoted Recorded Traditions from His own memory and then explaining things.
It should be noted that, many of those who believed in Bahaullah, were Religious Scholars, who had spent many years in school to learn Religion, and in fact in the eye of those scholars, Bahaullah's knowledge was superior to them, and that Bahaullah provided deeper understanding of those verses of holy Books and Traditions. So, if those scholars who spent years to learn Religions saw their own knowledge subordinate to Bahaullah, then the fact that according to history, Bahaullah did not go to school to learn, and did not have the books to read from, and yet knowing them in details is a mystery. I am not sure how familiar you are with the Islamic recorded Traditions, but just to give you an Idea, there are literally a thousands books. Just imagin several time volume of the Bible or Quran. In Islamic Schools they study them. But Bahaullah had been able to quote from these books accurately right off from His mind.
If you read at least Book of Certitude you would get an idea, about the knowledge of Bahaullah with regards to Religious Traditions. It often takes a few months to read it, but according to history Bahaullah wrote it in 2 days.
Now, let me give you more information.
As i mentioned before, Bahaullah wrote about 17000 works. And also Abdulbaha wrote some 30 volumes. All of these in Bahai view are infallible Revelations. As you know, Bahai Faith has many enemies specially among the Shia Clergy in Persia. So, they have done so much efforts to find a mistake in all these Bahai Scriptures to refute it. Because all it takes is to prove there is a mistake in them, to prove it is not divinely revealed, as God does not make mistake. In many of these Books, Bahaullah or Abdulbaha from their memories quoted from history, recorded traditions or verses of holy Books. But I still have not seen that they have been able to prove any errors in them. That adds more mystery to this. Also, you may not be familiar with classical Arabic. In Persia, the Muslim Scholars spend many years in school trying to learn it. Bahaullah wrote in Arabic so rapidly and fluequently, without mistakes, and Khalil Gibran, an Arab Writer, after seeing Bahaullah's writings, said He has the most eloquent Arabic. Despite the fact that Bahaullah did not study Arabic according to history. I do not mean that you have to believe in Bahaullah. I am just providing historical information, and not just speculations. Now think about this, that Bahaullah had so many enemies, who tried and still try to refute Him, so, if they could find where His learning comes from, but to the best of my knowledge they could not. If you find some real information, which is not speculation, I like to learn. It is irrelevent if those Recorded Traditions which Bahaullah quoted from them are important or not. Neither it matters if Arabic is an important language or useless. What the point is here, still to have their knowledge, one must spend years to study and learn, and even then, people usually make mistake. But Not Bahaullah