I do not know the answer to this question but I do know that I have a very poor back mobility and stretching did not work for me.
There are pro and cons regarding stretching on damaged disks.
Some said if done correct stretching may push the bulge of the disk back.
Some said that stretching will further aggravate a damage disk and in this case a stiff stable back is better.
That mean to do only exercises that involved no spine movement and even during walking to have a slight contradiction of mid section muscles in order to assure spine stability
I am curious about other general opinion regarding this issue