Kauppias, what is this OW weakening you are talking about?
On Finnair webapages,
Q&A section, it still says separate ticket on oneworld flight is OK:
I’m travelling to Malaysia, and the first flight is operated by Finnair. Will my baggage be checked to my final destination, or do I need to check-in again at the transfer airport?
Finnair checks your baggage to your final destination if your journey is on the same ticket or your connecting flight is operated and marketed by Finnair or another oneworld partner. When baggage is not checked through for a connecting flight, it is delivered to the baggage claim area. In this case, please collect your baggage and check it in for your connecting flight.