A lot of people's ears perked up when they heard this idea spoken of in the lines of Max Brooks' "World War Z" and, struck with the sense of it, they wondered if this was actually something Israeli authorities did, or if it was an invention for the book.
Robert J. Joustra wrote on The Center for Public Justice website that it is true, sort of. He pointed out that more minds don't always make better decisions: "Following the recommendation of the Agranat Commission in 1973-1974, Military Intelligence established a Control Unit that was expected to play this role of the devil’s advocate. Its responsibility was to produce a range of explanations and assessments of events that avoided relying on a single concept, as happened in 1973." The idea and role exists, but Brooks modified it out of his own mind, it looks like, carving the idea into "The Tenth Man."
Joustra quotes Irving Janis as he writes about this valuable role in groups, which Joustra terms "loyal opposition."
Janis: “The more amiability and esprit de corps among the members of a policy-making in-group, the greater is the danger that independent critical thinking will be replaced by group think, which is likely to result in irrational and dehumanizing actions directed against out-groups.”
The Yom Kippur war was a surprise to Israel and therefore a striking failure of the authorities' intelligence forces (the section responsible for this was the Research Department called "Aman"). I don't have any source for this, but one commenter on a discussion on Stack specified that there's a unit within the IDF called "Ipha mistabra" whose purpose is to doubt everything and come out with alternative theories to every regular theory the intel section has.
There is precedent for this strain of thought in Jewish history. The Sanhedrin was opposed to killing even criminals as an act of "punishment," and it happened very rarely. Among other failsafe's against wrongful conviction, there was a rule that the if the assembled judges came to a unanimous guilty verdict, the accused would be freed. The reason was that if none of the judges could find anything exculpatory about the accused, there had to be something wrong with the court.
The Vatican also has something similar, but for a sort of opposite purpose. It is a failsafe against electing saints popularly instead of on merit. This was the "Devil's Advocate" role given to one of the panel during canonization of a new saint. Their job is to find flaws in the person's character and their required miracles during the process of review.
However, even when the stakes are high, a dissenting voice might not mean anything. In the Yom Kippur war itself, the Israeli's, comfortable and confident after repeated illustrations of their military superiority and their neighbours making threats of invasion and not following through on them, found themselves on October 6, 1973 facing 1400 Syrian tanks and 1000 artillery with a rushed-into-place reserve force bringing their number up to 177 tanks and 55 artillery, and the Syrians rapidly shot towards Israel's northern settlements before being stopped, and in the south Egypt crossed the Suez Cannal and destroyed tons of Israeli tanks and aircraft with their new Soviet weapons; All this happened despite 6 months of evidence of a war buildup, doubts among two of the 3 top Israeli army chiefs, and two serious warnings from one of Aman's (Israeli's intelligence service mentioned above) - but just one - researchers, which warnings were both ignored by his senior officer, and even when photos showed the unprecedented military buildup on both borders and Jordan's King Hussein called the Israeli PM to warn him, Israel did almost nothing to prepare. They didn't think it would happen; they already believed something else.