I can confirm this trick is the key for showing JAL flights. I called 3 agents and none of them could see the JAL flights that I saw. One agent even called the Help Desk and they were also helpless. They said something like we were having problems with showing JAL space, they didn't offer us those flights, etc. I was about to give up but decided to try again. The fourth one was able to get the flights. When I asked her what she did, she said the same thing "open JL reservations on a new screen". When I called back to amend my booking, I told the agents to use the trick and they could see the flights just fine when trying that.