That appears to be the case. The filter applies to airports on the aeronautical data list, but maybe not to any files you've imported. I have a couple of imported turnpoint files, but none are far away enough that I have them filtered out. Although the airports that I have in the turnpoint file and are also in the aeronautical data list show up twice. I suppose I could turn the aeronautical data off, but it know a few fields that our turnpoint list doesn't. So for now I just live with the duplicate listings.