MP2637 Ilim set

From figure 16 in the datasheet,a 5.1K resistor is added between D+ and Vin,but usually the usb device port should use a 1.5K resistor pull up to 3.3V,is it wrong here?
Another question is if the 18K and 90.9K resistor in parallel to GND,
the equivalent resistor is 15.02KΩ,which is smaller than 16.5KΩ described page 31.

Can I use a single resistor from Ilim to GND ,if I have both wall charge and usb charge situation?