Not sure which part you're referring to, but I agree. The u2if firmware I'm using has an interface type that generates the addressable LED bitstream with the RP2040's PIOs. The host software dumps the pixel color values over USB CDC into a buffer on the RP2040, then when it's done the firmware tells the PIO to read the buffer with DMA and stream out the precisely timed LED bitstream.

Currently it's running in "one light string per PIO" mode but there's an inaccessible mode where one PIO can do up to 8 strings simultaneously. The pins have to be physically adjacent, though, so it's a bit more difficult to set up in a generalized way.