Set "Pot Mode" to "Passthru". Select lowpass filter. Set it to 164 with the Frequency knob. Select Layer B. Select lowpass filter. Set low pass frequency to 64 with the Frequency knob. Select Layer A. Select lowpass filter. Turn the Frequency knob and look how the value JUMPS. It does not act as "Passthru" anymore.
Short version: When switching from Layer A to Layer B and vice versa, "Pot mode" "Passthru" does not work as intended, it jumps.