Bug report for 8.2.3c:
When org-agenda-sorting-strategy is set to deadline-up (or similar values), the Global Todo list always places non-timestamped entries at the beginning, even when org-sort-agenda-notime-is-late is true. This is inconsistent with the behavior when org-agenda-sorting-strategy is time-up.
I believe the problem is that the org-cmp-ts function copied a line from the older org-cmp-time function: