[Brightcolours]

I would not care about that any... for example, what relevance does the equivalence to FF - a format I've never been using and likely will not be using in any foreseeable future - have for me? Not any more than MF or LF for that matter. Of course, everyone's case is different...

 

I tend to refer to my lenses not by any FL or much less their equivalence to anything, but as "DA WIDE", "DA LONG", "DA WIDE FOR DARKNESS" and "DA ULTRAWIDE". There's also "DA LENZ TO PUT IN DA BAG JUST IN CASE", which is the 24-85.  Soon maybe to be joined by "DA CURVED".

Still, for you it is handy to know that iPhone 6S' back camera lens is equivalent to "DA WIDE", but not so much to "DA WIDE FOR DARKNESS".

Or, that when you read, out of whatever interest, about for instance a Fuji GXF, that "23mm" means more or less a lens between "DA WIDE" and "DA ULTRAWIDE" (18mm FF equivalent).

So, still equivalence, but you pick a different reference point. 

 

Equivalence is not about FF, but how does X compare to Y. You can pick X and Y freely. To make things easier, usually people pick FF 135 format as Y.