Most people cannot accurately gauge how much weight they’re putting on a foot even if they’re just grazing the floor with it. Putting any weight on an operated foot or ankle can do damage to the repair that’s been done. Bones need time to heal. Plates or screws that may have been added during surgery need the bones to heal around them. Adding weight too soon can interrupt this important internal healing process.
These days many folks are sent home from foot and ankle surgery in a walking cast, depending on the injury and surgery.
The idea is that walking improves circulation, and circulation speeds healing.
If you have doubts, consult your physician/surgeon.