on the grounds that any weather mentioned in METAR, TTF and TAF would be intended to be considered "at", as that is the whole purpose of those reports/forecasts.
"The qualifier VC will be used to report certain significant weather phenomena in the vicinity (between approximately 8 and 16km of the airport reference point) of the airport."
What about RETS? Are you also required to carry fuel for that? I would be interested to see the TTF that the OP was looking at.