Issues don't update "Updated at" when a development commit is made on that issue number (via Github).
I have tried to achieve something similar using Workflow and triggers, but when the issue is already "In Progress" it doesn't trigger a transition. I added a custom field and tried to append something to it, just to trigger an update, but the transition doesn't fire.
Would be handy for the JIRA to say it was updated when a commit is made. The count of commits does go up. I just can't easily show when the last commit was made without drilling into the development page.