You're confusing a tax liability with an offset to UI benefits.
I think that 1099R's issued for 401K withdrawals might look different from 1099R's from IRAs. However, I don't have the paperwork to prove it because I have never taken a withdrawal directly from a 401K.
You can get rental income from the spare room in your house, dividends, and interest. All of those are taxable, but they do not offset your UI benefits.

