Yes quite are correct; I stand corrected open descent will maintain idle and make at time wild V/S adjustments to maintain such, open climb the same. You can set selected speed for what you want, idle or climb. For a climb using selected speed, or managed to not necessarily going into a thrust climb set or conversely idle in decent using V/S.
Example: area controller London giving small altitude changes climg or descend by 1 or 2 thousand foot increments, open climb/descent is shear misery. Even in a long climb or decent I find it poor airmanship; as you go though wind density and temperatures change to sit there and accept large variations in V/S.