Authors versus Characters

I've just finished reading The Almond Tree by Michelle Cohen Corasanti  (It's important to give the author's name here.  Three books with that title can be found in Kindle Store.) This one is a novel set in Israel,  an historical saga spanning 54 years ending in 2009.
Strong threads of determination, optimism and family values run through the  narrative consisting for the most part of only too believable tragedies that beset the rural Arab-Israeli family at the heart of the story.
I found the story gripping and was impressed by its historical accuracy.
However, I have one query which is relevant not only to this novel but to many others where the action is seen through the eyes of a single protagonist and there is no author narrative.
A character in the novel  passes on information which he/she believe to be true and which supports the main thesis of the novel, yet  nowhere in the book is the misinformation denied so the reader is left with the impression that the falsehood is historically accurate.
Here is an instance. The children are listening to nostalgic conversations between their uncle and their father, I quote,
'From these talks, Abbas and I learned how in the nineteenth century Palestinians developed the Shamouti orange, also known as the Jaffa orange.'
The political importance of this statement is that both Arabs and Jews claim to have bred the Jaffa which proved to be a major element of  19^th and 20^th century prosperity in Palestine and use it to assert their right to the land.
In historical fact the Jaffa orange was developed neither by Palestinian Arabs nor by Palestinian Jews but by Germans or more strictly, as the reunification of Germany had not then taken place,  by a group of Christian Westphalians who sold their surplus nursery stock to fellow citrus growers, both Arab and Jewish.  All three grew rich on the export trade the Jaffa orange provided.
Now, I believe it is quite legitimate for an author to allow a character whether deliberately, or in this case unwittingly, to pass on unreliable information.  My query-  is it legitimate, in an historical novel for the author to allow that information to go unchallenged?