[Sigh-on-Rice]

There is an update there with a comment from Subaru.

Just to clarify, this is a simple ECU mapping issue that is fixed using a re-flash of the ECU and it is an extremely rare condition found in a small number of US Subaru BRZ vehicles. Customers will be alerted to the issue by a check engine light.
The condition causes no damage to the engine and a TSB is in-process.
It is not related to mileage and no replacement of the ECU is needed at any mileage to rectify the issue, the ECU re-flash is the fix.
The issue is caused through the ECUs reaction to normal mechanical variations and is statistically very small. There has already been a fix at the factory level and it was an ECU mapping change, not an engineering process or mechanical modification. The ECU mapping was too restrictive in the original mapping set up.

What I don't understand is, if the fix is as simple as they say, then why are there so many people with their cars in shop...?