Up or down thrust to correct pitching while hovering is done to correct a design flaw: the relationship between the thrust line and the center of gravity. If there is too much of a difference, the plane pitches up or down while hovering. The same thing could be accomplished by leaving the thrust angle zero and moving the battery up or down on the airframe to get rid of the pitching.

Adjusting the thrust angle should ideally be done after the above to correct for any small aerodynamic asymmetries in the way the slipstream hits the tail.