The situation is not analogous. The definition of "Palestinian People" is not a purely a historical question so there is no need to cite only historians on that point, citing experts in diverse academic disciplines is appropriate. Unlike the Causes of the 1948 Palestinian exodus, which is a historical question on which copious academic experts have been published. Secondly if something is "prima facie" RS, it does not mean that it necessarily meets RS requirements when we look closely at the source (for instance if we see that the source is a non-expert in the field citing a known propaganda source). Thirdly Sundquist has only just been added to the article, so the source should stay out until consensus is established.