I think he fears that the main effect of a UBI-type program will be raised rents, it will be a transfer of wealth from members of the wealthy class to other members of the wealthy class, something of a Wework-style boondoggle.
That is, you give out $X to everybody, but everyone making over $Y+$X total has $X added to their taxes.
This feels a little silly on a but-you're-doing-things-twice level, but it lets a UBI program and taxes both operate independently without needing to cross-verify things, which allows for lower overall staffing and less in the way of possible bureaucratic loopholes for people to get stuck in.
In software engineering terms, it reduces coupling. We do the same thing with Social Security: benefits are taxable so recipients with high incomes end up getting checks and paying some portion of them back, but that's simpler than trying to have the SSA figure out everyone's taxes.