I can definitively say that this is an Alaska IT issue. I have been monitoring this current thread as well as this one regarding FJ award seats for the last few days and have been anxiously trying to confirm recently opened J availability. My booking has a stop over in NAN and then continues on to SYD at a later date. I was confirmed in J from North America to NAN, but only Y was available for the leg to SYD when I booked. With the recent dump of FJ availability, 2 seats were showing up on Alaska's website in J. AA showed this same availability as well, and I was able to click through on AA's website to the payment page, so I reasoned it must exist. I called Alaska over 10 times, and each time the initial agent would say it wasn't real availability. I would ask them if it was possible to check in SABRE, which some would do, and others admittedly didn't know how, still no luck. Sometimes I would be able to get them to transfer me to international or "global" desk, sometimes not. I would HUCA every few hours for the last few days, because I believed that if AS and AA both still showed the availability, it must really exist.

Today, the first agent I talked to put me straight through to the "global partner desk" where the very helpful agent initially hit the same wall as everyone else. Then he tried to "long sell it" in SABRE, and it still wouldn't confirm. He put me on hold for a few seconds, and when he came back, he had it done and confirmed. I asked him what he did to get it to work, and he said he tried to long sell it again and it confirmed. He didn't know why it didn't go through the first time. I have confirmed that it took on FJ's website, and have already selected seats.

In a past life, I worked as an agent at two of the remaining big three and I have been trained in SABRE, SHARES, and DLTERM, albeit many years ago. I can recall scenarios where availability would show as 0, but if you tried to long sell it anyway, all of a sudden it would show up. I have no idea if the availability just wasn't current to the second and somehow requesting it caused the computer to recheck and discover it really was there or what, but I suspect that may be the issue here--that there is some sort of communication discrepancy between what AS shows and what is really there. Hopefully AS can get this issue addressed and fixed, and of course YMMV. In the meantime, I can say with absolute certainty that it can be done if you get the right agent.

TLDR
I saw availability on FJ in J on both AA and AS websites. Every agent told me it was phantom space, but I would HUCA until I got an agent at the global partner desk who was willing to try booking it in SABRE, and it worked!

Edited: Spelling