Add comprehensive remark

SabreTools.Library/DatFiles/Filter.cs

@@ -1965,6 +1965,16 @@ namespace SabreTools.Library.DatFiles
         /// Filter a DAT using 1G1R logic given an ordered set of regions
         /// </summary>
         /// <param name="datFile">DatFile to filter</param>
+        /// <remarks>
+        /// In the most technical sense, the way that the region list is being used does not
+        /// confine its values to be just regions. Since it's essentially acting like a
+        /// specialized version of the machine name filter, anything that is usually encapsulated
+        /// in parenthesis would be matched on, including disc numbers, languages, editions,
+        /// and anything else commonly used. Please note that, unlike other existing 1G1R 
+        /// solutions, this does not have the ability to contain custom mappings of parent
+        /// to clone sets based on name, nor does it have the ability to match on the 
+        /// Release DatItem type.
+        /// </remarks>
         private void OneGamePerRegion(DatFile datFile)
         {
             // For sake of ease, the first thing we want to do is bucket by game