GitHub allows to see when the commit has been authored, in addition of the commit time. It's useful to understand the chronology of a code, by opposition of the chronology of its integration in the master branch.
More often than not, I go to GitHub to check this information (where I'm frustrated with "23 days ago" who asks to perform date calculation or "one year ago" with a wonderful preision) or uses manually `git log.`
It would be more convenient to get this info on Diffusion.
UI rendering could be like the commit date (phui-status-item-note), and only if the authored date and commit date diverge.