How many supervisors on here believe in their team members learning from their mistakes?

The simple answer in we don't learn from our mistakes.
We learn from the correction of our mistakes, no matter big or small.

Simple answer: Everyone learns from their mistakes In a general perspective, it depends on the impact of the mistake they have made, generally, if things went terribly wrong, a good employee will establish something to prevent the same mistake from happening (structured or unstructured), but for small mistakes, some will not bother to not do it again.
As a supervisor, you need to be on top of things, you shouldn't micromanage, but you need to constantly evaluate the capabilities of your team, some would need constant attention, and will require lots of audit work, others would not need supervision at all.
P.S.: Learning is sometimes dependant on industry, and the tolerance it has for mistakes, which sometimes reflect the measures taken to prevent mistakes.