I am just saying the elasticity of the tissue is greater under lower erect states (absent rigidity) and more conducive to expansion. As rigidity creeps in the pressure characteristics cause the chambers to begin peak expansion or your tunica is reaching its maximum expansion. When rigidity is present your penis is taking its natural and full state, in this condition it is difficult to augment change. The physiology becomes indestructible it is turning into superman or penis, you must do your activity when it is Clark Kent.
When you are doing glans work (this is all I do, everything else comes along for the ride), you cannot optimize expansion of the corona without 100% engorgement and a relatively limp state. When you are fully engorged and grab the base tight you have a full erection, your tight grip has taken place of the pressure gradient and valve constriction (present during an erection). Usually the jelq activity will work you to a level of erection and than you let the condition abate by stretching your sack or pancake the penis on a cold surface (this will diminish the erector). After you cycle through a couple of these conditions, your penis becomes annoyed at becoming erect and no action so he no longer participates and you can get a very effective workout.
One mans 80% erection is another mans 70%, there is no empirical way of measuring this state. And when you get below 50% there is little consensus between penis’. Rigidity is the bane of PE, tissues must be elastic and blood volume copious for maximal opportunity for deformation. Hang long, hang tough.