From that photo, I can see 2xWS2811 drivers, but 4 LED elements, 2 RGB (centre “white”) and 2 WW (centre “yellow”).
Each WS2811 can drive 3 channels, typically R, G, B but it’s possible to attach any colour LED to any channel (even WW). The chip has no idea what’s attached, it just outputs the current request you send via the data stream for each channel.
Probably the pairs of RGB and WW LEDs are put in series so they can run at higher voltage (helps eliminate voltage drops). The RGB LEDs are driven by 1 chip using RGB channels and the WW are driven by a single channel (one of the RGB) on the 2nd chip.
You can test by varying the Red only on one of the “white” LEDs in your segment (the odd ones?) and then try varying Green only and Blue only. You should see one of the RGB channels controls the brightness of the WW and the others do nothing.
One last possibility: there’s more circuitry on the back side of the board, we can’t see.