I do agree that $68k as a salary requirement is fairly reasonable, though – but it's much higher than the "average" salary for a Japanese person.
US$68,000 is enough for a very comfortable life there.
People may not agree with the above, but that's what they want, and I can't blame them for wanting good for their country.
EDIT - you changed "poser" to "pretender" which was a small improvement. It's polite to make it clear that you've edited a comment if someone has replied.
Apart from the tourist aspect of it, the point of a digital nomad is to save money on rent, food and taxes, not to spend all your money in a foreign country.
Of course, a business hub, or a technological hub can attract digital nomads punctually, even if accommodations are more expensive.
Now Japan has a problem with its age pyramid and desertification of its country side. So it should be possible to attract digital nomad for longer and cheaper stays, even if they don't have a lot of money (to spend in Japan), at least that's good for the young body count, and perhaps they'd eventually fixate and have families. But again, this wouldn't be a six-month thing, they would have to add more incentive (free or $1-house in the countryside with minimal occupancy, good internet connection (I don't know if Japan has 100% territory fiber coverage) (that said nowadays there's Starlink), etc.
Spending money on living expenses, including rent, and touristy stuff is indeed spending money in the country. And if you are well paid then that may be more than the average local: the threshold for this visa is $68k while the average annual pay in Japan is apparently $41-45k.
"Digital nomad" can encompass many and any thing. It seems sensible to target higher earners if they can. It's not about how nicely you think you can live, it's about the benefits a country seeks in letting foreigners in.