The L5 nerves are affected with an isthmic spondylolisthesis of L5-S1. This is why this surgeon thought you should be developing symptoms on the top of your feet. The L5 nerve essentially stops at the top of the foot but the inside bottom of the foot (big toe side) could also be affected.
The feeling of walking on glass (allodynia) is generally from an actual intrinsic nerve root injury and not from nerve root compression. The difference is that when you remove compression from a nerve root, the compressive pain will generally abate but with an injured nerve root, this pain will generally remain. Read “chronic radiculopathy” and “nerve damage and healing” on this website.