According to rule 13.1 "The air flow meter must be stock genuine
Porsche OE and be unmodified but can be adjusted (tuned and wiper bent to maintain clean
contact with track)."

It seems as if bending the wiper to have contact with track would correct for a worn track.

How can having the cover removed and having the AFM "tuned" at a speed shop with the car on a dyno to obtain a gain in hp not be modifying the AFM? What else could be done to modify the AFM?

There is an adjustment outside the cover to correct for lean or rich running conditions. Isn't that what Porsche placed there for that purpose?

Then would that mean tuning a DME is not the same as modifying a DME?

The term "modify" is referencing doing things to increase performance through material modification. An example is porting and polishing for better flow.

Bending the wiper arm corrects an issue that arises from years of use that would make the AFM perform erratic. Adjusting the spring tension allows us to tune the AFM specifically for each engine personality. A certain setting on one car may not be the best for another car even if they were all calibrated at the factory.

Changing the spring tension also allows tuning of HP/TQ around the power cap. An engine that is lower than the power cap that hasn't had a tuned AFM on the dyno can pick up some cheap/easy power by finding that sweet spot AFR for that engine. Its a very simple tuning allowance that is very useful.