VGC will fall behind if they don't start updating their total numbers to include digital sales when the big 3 release these numbers in their reports. Granted not all games can be accounted for but the big games should at least show both digital and physical sales when provided.
A prime example of VGC numbers being way off is Animal Crossing: New Leaf. VGC finally has the game at 6.35m sold (physical only). However, AC:NL reached this with physical and digital sales back at the end of Sept. ( http://www.gamnesia.com/articles/animal-crossing-new-leaf-passes-6.35-million-lifetime-sales1#.UvJ9hbTwq10 ). Nintendo recently released figures showing that the game is now at 7.38m ( http://www.neoseeker.com/news/24552-nintendo-2ds-sells-21-million-units-animal-crossing-new-leaf-sells-738-million-worldwide/ ). So basically the game is at least 1m under the total sales of physical and digital.
Technically it isn't undertracked if one just counts physical sales. However, I believe that VGC needs to start implementing some plan on how to account for digital sales or at least update total sales when they are released in reports. There should be at least an * by the total stating physical sales only. If VGC doesn't start doing something about digital sales then the gap in numbers is just going to continue to grow. I suppose this doesn't bother most people on this site but in the future it will probably bother more.
