This pose has many variations: spine more or less extended, arms overhead, or hands on the back as in salamba sarvangasana. Some of these variations put more pressure into the spine than others. For example, when the arms reach overhead and clasp the toes, the scapulae upwardly rotate and move away from the spine, and weight falls into the upper spine. This variation can overmobilize the thoracic and cervical spine; there is potentially damaging pressure from the pushing action of the feet and, if the hamstrings and gluteals are tight, from the limited hip flexion forcing greater spinal flexion.
Because this pose can produce very intense flexion for the spine, especially the cervical region, it’s more important to maintain the integrity of the scapulae and cervical and thoracic spine than to get the legs to the floor; support the legs if necessary to protect the neck.