Cancelled date different from actual cancellation

When cancelling requests by users, it appears that the request is cancelled and indicates terminated, but then several minutes and sometimes hours later, the cancellation time is updated with a different time indicating that perhaps this request wasn't totally cancelled and there was residual clean up that was required.

Is this because the concurrent manager updates the termination time after performing any rollbacks? If I check the diagnostics screen for the request it will say something to the effect that the Internal Concurrent Manager terminated the request. Should we always followup with user-terminated requests to make sure they were actually terminated?