tl;dr – The airline’s partnership failed to make it one year.
A notice on JAL’s website reveals that the partnership between Japan Airlines and JetBlue Airways will terminate on March 31, 2026.

After this date, you will no longer be able to book JAL fares using TrueBlue points.

JetBlue was the recent winner in a battle-royale style edition of our weekly series – Deals I’m Booking That You Should Too. I was able to purchase TrueBlue points to book two JAL business-class flights from Tokyo to the US (LAX) for $ 2,674.56 or $ 1,337.28 per ticket – a savings of $ 3,000. per ticket off the cash price.
Sadly, it seems future redemption opportunities like that one are soon to be sunset.

The specific details of the termination, including refund conditions, are as follows:

Other loyalty programs that tend to have decent saver-fare availability for JAL premium cabin fares are Alaska Atmos Rewards, American AAdvantage, and Qantas Frequent Flyer.