If the verse omitted either one of the two actions (to rise and to remaining standing upright) we would not get the full picture of the dream Yosef is describing. If the verse omitted "rose up," one might think the sheaf was already standing and that it could have been placed in that position by human agency. Therefore, the verse tells us that it "rose up" specifically at that time and by its own agency.
The word נִצָּבָה indicates further that the sheaf remained standing from its own agency, that is, it did not fall down, and it did not lean against anything, and it did not require a human hand to hold it up. The verb נִצָּבָה also connotes endurance in standing upright, perhaps as a hint to Yosef's enduring preeminency among the tribes. If the verse ommitted נִצָּבָה , this element would be missing.
The two words together magnify the prophecy and the miraculous nature of it. It is a double miracle that the sheaf both rose up and remained standing (even though it was 'just a dream'). Yosef had to "rise up" from being despised by his brothers, sold, and imprisoned and then "remain standing upright" in a new rank and status within the tribes. For example, many (but not all) of the elements of being the first-born (bachor) are ultimately transferred to Yosef and it is this new, elevated status that endured.
All this is simply what I understand from knowing the difference between the two words (as Rashi explains) and from knowing the narrative context.