WingFlaps schrieb:

So an altimeter set to local QNH will always read field elevation *by
definition*.

Yes it may say that but it's being loose because it forgt to include
the "barometric pressure reduced to MSL by application of the ISA".
Alltimeters are calibrated for the standard atmosphere. -right?

Right.

Think about it, if an ARFOR gives QNH how could it be correct for all
terrain if local temperatures differed? I covered this in my PPL tech
course -was this not covered in your manuals?

Think about it, nobody said it would be correct for all altitudes, but
just for one altitude: the airfield elevation.

just in case you still don't see it, from Wiki:

Wiki, the ultimate authoritative source.

Hint: Look up the difference between QNH and QFF.