That doesn't track. By that logic, a UBI would provide disincentive for ANYONE to work.
Right, it definitely will do that. By raising all incomes, UBI reduces the marginal value (you value the first dollar you earn much more than the 100,000th) of all dollars earned. Some number of people will decide that they value their time more than low income jobs and will reduce their hours. I don't remember exactly but I think the UBI experiments we've tried showed this does happen but don't remember the details.
What the Universal part also does is avoid depressing the marginal value of work. Today, you work and extra hour, get and extra $X in income, but reduce that income by $Y in reduced benefits. In pathological cases, $Y is greater than $X, and that's the poverty trap. But even if $X > $Y, ($X - $Y) might not be enough to make the extra hour worth it. With UBI, $Y is $0 so it doesn't have this effect. I'm sure someone who actually took Econ 101 (read: "not me") could put this into math using supply, demand, floors, and rates.
How large these effects are is the trillion dollar question.