Also, to note, spouse credit may be given, which is a recognition credit and effectively would be akin to acknowledging the donor. I believe to have a flexible solution you would need the ability to select which soft credits to include, and not just the default 'all recognition recipients'

The current process will assign the letter to the donor even if recognition recipients only is checked under circumstances where the donor is also credited (for example, if you credit your donors with a 'hard' or 'donor' recognition credit).