Could you elaborate about what the GET /areaPrices attribution `confirmationStatus` means? Specifically, what does an unconfirmed price reflect? How likely is it that it will change significantly?

The preliminary (unconfirmed) results are the Auction results that are first received. These are announced to the market and published to the APIs at 10:45 UTC. These preliminary results still need to be approved and validated by the TSOs. On a normal day, this will happen before 11:00 UTC. After that, preliminary results become confirmed and have "confirmed" status.

We do not remember any cases when preliminary results were not approved by the TSO. So you probably should not expect many changes between unconfirmed and confirmed results.