I would define Standing rigging as:- All lines/wires used to support the mast.

I believe the ISAF definition is pretty much in line with that. Would have to check to be sure.

So I guess the issue comes down to which of the F16 rules has priority. 1.7.2 states you can adjust the diamond tension during a race.

However in the "main rules" section it's stated that: The rig may not be trimmed between start and finish by other means than sheet, downhaul, outhaul, traveller, mast rotation and halyards systems.

The above rule seems to contradict 1.7.2

I think its a big stretch to say that you are using a sheet to adjust the sails... via the diamond tension.