Unless you're someone with a lot of flexibility of when you are going to fly and can buy Lat or PY Flex and move around if/when you see R space open up on a different flight or a different day ... or can wait around to see if your eUp clears at some point if the loads are light enough, and then cancel and rebook something else if it does not ... then most of this doesn't really help. Travel "influencers" who are providing "hacks" aren't fixed to travel on a specific date.

The bottom line for the OP is if they want an eUp their best odds are a PY ticket, and even then they are gambling (how many people with higher status than them in PY looking to upgrade? how many J seats available?). I have been to Japan three times in the last year (never mind previous years), once in paid J and twice in paid PY, and as an SEMM I've gone to the gate for my upgrades when I was in PY. But this is almost certainly their best bet if they need to fly on a specific date.

They could also try a bid upgrade, again, playing the odds as nobody knows what will be accepted. Or they can see if an LMU is offered, and again playing the odds if it is offered and if so for a reasonable price.