Just got back from LAX-HND RT, and that's basically what my wife and I did - booked our flight when news came out they were reopening (booked around September 2022?), immediately requested SWU on both legs for my wife and I, and rolled the dice. Flight from LAX-HND was 100% full, I've got over 300k LP, we were #6 and #7 on the waitlist, and not a single person got upgraded. I chatted with the FA during the flight, and he stated he'd been doing that route for a month and the daily flights had been 100% full (with a standby list on the app too) since the beginning of the year and likely continue to be since the country recently opened and the exchange rate is really good. On the way back home, SWU cleared around T-24 before check in, and 1 person on the waitlist cleared into J.

Ultimately, if you want to go to Japan, not getting seats in J won't make a huge difference so just go even if you're seated in MCE. Yeah, it's nice to fly in well rested, but it won't make much difference if you land at 5AM and you can't check in until 3PM. Hang out and eat at the LAX Qantas lounge, and HND JAL F lounge before your flights to unwind. Lots to do outside of sitting in an airplane and it was 100% worth it.