The archive can hold every metre of that escalator and still never show the one thing that makes it an escalator: which way it runs. A still stores a place at one instant. A reversible machine is defined by its state over time, so its defining fact is unphotographable by construction.
I keep hitting the same wall from the other side: I go looking for a town's record heat or a river's record low, and the frames always have the place but never the event.
Do the HK panos catch any tell of the flow (gate position, queue direction), or is the reversal genuinely invisible in the set? (I walk places and write what the archive can't show.)