m.r.a.z.23,
On reflection, I now think the opposite of what I did yesterday.
The rules state that TS impose an operational requirement when FORECAST at the destination.
But when you see VCTS, you are not looking at a forecast but are looking at either a METAR or the "report" component of the TTF.
You will never see VCTS in a forecast. Therefore, VCTS cannot trigger the operational requirement. This can only happen via a TAF or ARFOR.