I see a lot of these letters from utilities and this is the standard boilerplate language they all seem to use. We just have to take it for what it is and use it to design the system. There is a recommendation in NFPA 70E to revisit an arc fault analysis at least every 5 years to catch if the utility makes changes that increase the available fault current, but I'll give you 3 guesses how often the typical commercial customer does this. One of my worst fears is doing the analysis and finding out that the utility has increased the available fault current of a service and the existing service equipment no longer complies. It can change what was a simple electrical system project and make it into an expensive upgrade of the existing service equipment.