No lumbar flexion beyond 60 degrees is not contraindicated, pure contraindication is combined rotation and sidebending which creates shearing and torsion forces to the disc. End of range flexion(EOR) is contraindicated also becaise this maximally opens the space between the intervetebral sements(veretbrae) placing maximal stress on the PLL, as well as forcing the disc posteriorly.
Oopsy! In exercise physiology world loaded flexion and rotation is contraindicated full stop, not just for those with disc herniation. Dr. Stuart McGill taught me that, not personally, but his research.
I thought you were looking for something really different. You will notice, though, that I reference the cause of the herniation in the last sentence of my post.
Thank you Chris, for challenging us with such thought-provoking questions. It, encourages me personally to continue to be proactive about educating myself.