OP is correct. A lower position is better for the lower back. I think the lower position opens the aft edge of the vertebral joints, which eases pressure on the nerves which exit the spinal column. My understanding is that nerve pressure is what causes the pain we call sciatica. I have one fractured and healed vertebra, thin disks, arthritic facets, and lumbar stenosis. I ride my road bikes with the maximum drop to the bars which the frames allow and riding these bikes is the best back therapy there is, although hiking in the mountains is good, too. The combination usually keeps my back pain-free. I've done 18 hour rides and 10-day unsupported backpacks as an old fart. It's all therapy and it takes a lot of therapy to keep me going.