Stacked insurance: only need it on one car to apply to all?

I find this a truly confusing topic. Stacked Auto insurance. I live in Florida where default is stacked unless you sign paperwork otherwise.

My question is this: if I have multiple vehicles, say three for example, do I only need to purchase stacked insurance for one of those because it covers the other two? And what I mean by that is if I were to have an accident in one of the two vehicles that is not the stacked vehicle, would the stacked benefits apply?