MLCC DC bias voltage effect on AC?
Capacitance has a certain AC impedance at certain frequency.
DC bias on a MLCC causes change in capacitance.
Thus, change in capacitance changes the impedance for AC signal. If you select the capacitance so that the impedance does not change much, then it may not matter.
This is exactly the reason why even for basic voltage regulators, you need to select the MLCC capacitor capacitance and voltage rating so that you get the required effective capacitance even with the applied DC voltage bias.