the patch didn't do anything, but we are getting close to the solution
I noticed I was in the "Artists" view while you are in "Album Covers" view
so I switched to Album Covers view too, and indeed the extra line with the virtual tag appears there
Although now tracks are not grouped by Artist anymore, but by albums, and so the virtual tag gives the count of track in each album, not the count of tracks for each artist as total
then I tried the "Sort by" and "Group by" options, but it doesn't change the grouping by albums into grouping by artists, rather than just adding a extra box between all the albums