Ah – Date Added – found it, though I’m not sure how it’s defined.
In any case, seems to be the same as Created And Modified - all three appear to be reset on each use of Hook.
All 12.39 in this case:
and if I launch and close Hook again, now all 13:44 today.
(macos Mojave 10.14.6)
(And no plists in that folder have any differences between their Modified, Created, and Added dates)