The Sin of the "Spies"

https://www.etzion.org.il/en/sin-spies

According to the Ramban (13:1 and 13:27) and the Akeidat Yitzchak (77) it appears that the sin of the spies lay in overstepping the bounds of their authority, in their transition from being faithful reporters – which was the mandate given to them - to becoming advisors with their own independent views and evaluations – which lay outside the bounds of their mission. Indeed, such a distinction exists in modern intelligence bodies, where the function of the information gatherers is to report on what they have seen or heard, and that of the intelligence evaluators is to evaluate the situation or even to provide advice, on the basis of that information. In the transition from one function to the other they did indeed overstep their authority, but ultimately this was no more than a formal sin. Is this really what constituted the true sin of the spies?