Insofar as the poor are secretly employed in the grey market, poverty is also secretly not as big a problem as we think. You can't have it both ways.
The article asserts that people will do good things with the basic income, but the one statistic they mention suggests they won't.
[edit: read paragraph 1 to find the stat I cite. I've compared the numbers of poor and non-poor excluding children as well, it doesn't change the comparison much. https://news.ycombinator.com/item?id=2130441 ]