You may already be aware of this, but there is an Excel file called "thread.xls" within your Design Data\XLS\en-US (or other language specifier)\ folder. Any time you create a hole feature and specify it as a threaded hole, or create a cylinder/hole by other means, then add a thread feature to it, these features reference this Excel file for available thread designations that will fit the size of the specified geometry. Within this Excel file, only the tab for "ANSI Unified Screw Threads" contains a unique identifier ("UNF" or "UNC") within its 'Designation' data columns that clearly identify which are "fine" or "coarse". All others use different means to define which variations are considered fine or coarse, and do not include a specific identifier within their designation columns which can be used this way.
What you would likely have to do is build your own lists (by whichever means is best for your situation) of which variations are considered coarse or fine, then when checking threaded features, you can cross reference its data with that of either of those custom lists to determine if it is considered coarse or fine.
Wesley Crihfield

(Not an Autodesk Employee)