The reason being that Alexander did not recognise the potential intellect for a spiritual faculty at all; while to Avicenna it was like the 'fit boy' in Pickwick, always dropping off to sleep, remembering nothing, and needing continual excitation from without to make it understand. See notes pp. 122, 123, 129, 132, 135, 137, 142, 143. It must be remembered that Averroes also makes the active intellect one and the same for all men.
Of God and His Creatures: 2.76