Why does my Physical Therapist say "NO" to Uttanasanna /Forward Fold/Standing Hamstring Stretch?

So, here is the skinny!  Take a good look at the lower spine of this picture.  The lumbar spine can be observed between the last/12th rib and the ilium/top of pelvis.  In forward fold, the lumbar spine is in full flexion.  In a spine with a herniation, bulge or perforation, structurally the front part of the vertebrae is compressed the most which puts increased and unbalanced pressure on the disc which lies between each vertebrae.  Therefore, if you have a herniation, this means the already increased compression on the spinal chord or nervous tissue, is increased even more in Uttanasana.  Know, it is almost impossible for MOST people to remain in 'Neutral Spine' and achieve this type of mobility in the hamstring as seen in picture because the hamstrings attachment site is on the ichial tuberosity of the pelvis.  When the hamstring is lengthened to it's fullest extent, at the end range , this proximal attachment site will pull on the pelvis into posterior tilt.  This posterior tilt, forces the lumbar spine into flexion.  What is "Neutral Spine"?  Neutral spine is the position of the lumbar spine, that in a healthy spine has the equal /balanced amount of compression loads on the disc.  It represents a normal lordotic curve in the lumbar spine, meaning a small curvature.  No way around it, we have increased compression loads on our spine when we stand up against gravity.  So, in a spine with herniation, to prevent further injury, or pain, or increasing unbalanced compression loads, we work toward understanding and being able to be aware of when a neutral spine is necessary.  People with herniation, can build strength and stability by balancing out the anterior (front)muscles of the body with the posterior (back) especially as relates to the spinal stability.  It is not about never ever doing an Uttanasana ever again, it is about knowing what is good for your body at that moment in your life.  Understanding the biomechanics of your body, will give you the tools to question EVERYTHING and make intelligent decisions about your body regardless of what you hear.  Besides, it  is not that the PT is wrong or right, it is about philosophy and individual appropriateness at that time. Physical Therapists are highly skilled biomechanical assessors, value their input - know yourself.