If historical books and documents of any non-English speaking nation were translated into English, this might help to preserve this history because translation could be an effective way for the history to remain intact.
History and historical documents lack validity because what they narrate must comply with the values of incumbent political system unless otherwise it is written by a scrupulous historian living in exile. On this basis, what you have astutely suggested can be a fantastic move towards enhancing the credibility of historical reports.
The question, in my opinion, is to what extent the historical matter itself is recreated objectively, impartially and exhaustively. The English translation, of course, would provide wider accessibility, recognizing and popularity, but it can not be a guarantee of the truth and accuracy of the content itself.
In my opinion, the answer for such question depends on what definition 'historical documents' has, and what 'distortion' was meant.
although 'historical books', which are part of historical documents, are in most cases, if not all, written to reflect certain ideological perspectives regardless of the language that were written in. So, when these books are translated into a foreign language including English, their fundamental discourse function remains the same or does not change. In this sense, translation plays its basic role of communicating the same message said in the source document.
For 'historical documents' which have no doubts about their authors and sources-whether they are written, oral or pictorial- translation may affect their authenticity since there are text's distinctive features which are 'untranslatable'. So, I think preserving these documents in their native language is a part of preserving their history.
Despite any distortion in the historical documents (if any), it needs to be translated for the intact of history. Positioning the documents as what it is, that keeps the history, and having its translated docs will enhance the science resources.