This is why a program that at no point has any way, shape, form, or manner of phase-out is desirable. It fully and completely avoids any kind of problem stemming from colliding cutbacks. This is such a good idea and so wise, that it was baked in to the approach proposed above!
But if it doesn't ever phase out, it is really just a tax cut, and to be exact a tax cut. I'll take having to pay 7.5k less taxes (or getting an untaxed check for 7.5k from the same people I have to write my tax check to).
However, what you call something and how you structure impacts how people react to it. Call it wages and spread it over time and people react one way. Call it a bonus and hand it out once a year and people behave differently. So while it may be more correct to call it a negative income tax, this may work against the intended economic effects.