strange note re Third

Amazon tells me of a change in my pre-order of the new Portishead album:

We are sorry to report that the following item is no longer available from our supplier. However, we have learned that a substitute is available under a different Item number. You may link directly to our catalog page for the substitute using the URL beneath the unavailable item:

Ordered item: Portishead (Artist) "Third" Substitute:"Third" (Portishead)

Odd because how would I know if an item comes from a different supplier? How would I notice if a catalog number changed? Whatever. Took one second to pre-order from a different supplier.