Decoupling NR pin in REF54 creates a low pass filter in combination with the internal resistance of 13 kΩ to eliminate internal band gap noise. Unlike regular low pass filter at the output of the reference, connecting a capacitor on NR pin doesn't affect the output impedance hence extra buffer is not needed. Leakage of the capacitor directly impacts the accuracy and temperature drift. If NR functionality is used, choose a capacitor which has low leakage over temperature eg. Film capaciror, COG, X7R (MLCC) are recommended . Please note, using the capacitor on NR pin also increases start-up time.

Figure 8-2 Temperature Drift comparisio with Flim and X7R and Electrolyte capacitor on NR