IB never releases more than 2 J seats, in my experience.
Personal Experience: Long ago I was IB+ Platino and called them 3 days before a long haul (JFK-MAD) was scheduled to depart, I asked whether they could release 2 seats on points (I checked and J cabin was almost empty)... they did it (exceptionally, I guess, due to IB+ status and being years ago when having a status meant something).
Later on I moved out of Spain and I started flying in BA more and more, so I moved to BAEC.