What is the point of the phrase "at the airport of intended departure"
in FAR 91.171(b)(1)?

Interpreted literally, it would mean that while the VOR check done
with a VOT is good for 30 days, it is only valid for departures from
the airport where it was done. That makes no sense. Any other
interpretation that I can think of would be the same with or without
that phrase. What were "they" thinking?