I've received this email when attempting to upload my app to test flight, but I have a long description like "This app collects motion data to track user activity and provide accurate workout insights. Motion tracking helps improve fitness and health-related features." specified in the project.pbxproj file, which is where all of these parameters are (and where I've specified them in the past).
ITMS-90683: NSMotionUsageDescription
I think this may be a bug in Xcode (or there is something I need to modify in my build settings), but I have a standalone WatchOS app (meaning the only info.plist is for the watch), but I can see when looking into the archive, that although the info.plist inside of the watch product files contains NSMotionUsageDescription, there is another info.plist generated in a higher directory (presumably for an iPhone companion app if there were one for this project), that does not include that. Once I edited this file within the archive, Test Flight took it. Note that I have a few other permissions (e.g., for location) also only in the watch info.plist) which worked fine