Odd artistsort tag behavior

Hi:

I'll try to explain this as concisely as I can.

I have an album of various artists, not tagged as a compilation, and the album artist is David Sylvian.
On that particular album there are some cuts by Japan, a band Sylvian was in.
If I change the artistsort tag on the album to "Sylvian, David", this happens:
--- All of my David Sylvian albums turn up under S (fine, that's expected)
--- My one Japan album also turns up under S, even though I've set the artistsort on that album to "Japan"

Does this sound like what should happen?

THanks,
Doug