yosef: dreamer or prophet?

The Rambam asks: why was Ya’akov afraid “shema yigrom hacheit”, that he might have sinned and be unworthy of G-d’s protection in his encounter with Eisav (Brachos 4), when we know that even a conditional promise of G-d for good is always guaranteed to be fulfilled (Brachos 7)? The Rambam answers that there is a difference between G-d’s promise which is given to a Navi to articulate, which is guaranteed to be fulfilled, and a promise which is privately told to a Navi, which can be revoked if the recipient proves unworthy (see previous post here).

I thought perhaps this was Rambam may explain a point of disagreement between Yosef and his brothers. Yosef insisted on telling over his dreams to his brothers. Later, when the brothers plot against Yosef, they remark, “Now we will see what will become of his dreams.” The Ramban (37:20) elaborates – “If Yosef can escape from our plan, then surely he will rule.” This seems like an unwarranted conclusion; just because he might escape death, why does that prove Yosef would rule? I would suggest that the brothers did not doubt that Yosef’s vision was more than a chance dream – there was an element of prophetic insight to what he saw. However, prophetic insight is not always meant to be expressed verbally as nevuah. It was not the dreams per se which the brothers objected to, but rather they objected to Yosef’s relating the dreams, transforming his private insight into formal nevuah which carries with it the guarantee of fulfillment. The brothers thought Yosef’s dreams were a private vision which they held he was unworthy of seeing fulfilled, but if he emerged from their plot unharmed, not only would it prove their judgment of Yosef faulty, but it also would imply that his dreams were indeed a nevuah which would come to complete and guanateed fruition.