Album.sortTags argument ignored

[nbpf]

I am trying to get the album list view (<n> albums) sorted by recently added albums by using an "incdate" (incorporation date) tag. "incdate" works fine as an index tag but adding "incdate" to the "Album.sortTags" list of tags, see

   

has no effect on the <n> albums list view. By contrast, replacing "incdate" with another index tag (composer, work, etc.) has the expected effect. Any idea what is going on here?