Everyone making less than 138% of the federal poverty level (FPL) qualifies for free healthcare. I dont think most people would say that the USA has universal healthcare.
The same is true here. If you make $0, you get $12K UBI. If you make $24K, you get $0 UBI. Is that universal?
Assuming there's no other income tax on the first $24K you make, it's a bit aggressive but it's still a valid form of UBI and an improvement on the status quo.
This particular method is mathematically equivalent to both of them. There's no actual difference between "You get full UBI and you pay income tax on other income" and "You get X cents less UBI per dollar of other income".
The system could be as simple as "UBI, also income tax is 50%, end of description".
> The question isn't about mathematics, it's about psychology and politics.
That's valid, but when someone's roughly describing a plan I'll give them the benefit of the doubt and worry about whether it can be framed the correct way rather than whether they framed it right.
> In the second scenario, when do I get/spend my UBI money?
I don't know, every two weeks? So it's the difference between a $460 UBI check and a $400 paycheck, versus a $60 UBI check and an $800 paycheck.