I think sending it to everyone makes sense. If they would have set limits - the limits would be argued. This way everyone got it - take it as public education and ignore it if it does not apply to you.
I can say that I have never used a "local" Supercharger. But I have used Superchargers a lot this summer for three long road trips; Tucson-Napa
Napa - Leavenworth, Washinton, State
I'm thinking that the so-called filter has nothing to do with "local" but rather frequency. The trip to South Dakota required 28 Supercharger stops over 7 days.
Perhaps they went on percentage of total power used sourced from superchargers at any distance versus percentage of power sourced from home or non-superchargers. If this was over the past three months, my long distance road trips on supercharger power would account for about ⅔ of the all power I used, due to two road trips to California. Sounds like you may have the same scenario.
If that is the case, the filter they forgot was the distance from a person home that the charging took place.
As I mentioned in another thread, I did get a letter but don't charge at a local supercharger.