When using the LV bridge as passive rectifier (only diodes), the output voltage is equal to the gain (transfer function) times the input voltage.

If the LV Bridge is used as an active rectifier, then the MOSFETs switch later than the diodes conduct, which is why the average current in the output capacitor is not zero and the output voltage drops.

Added phase shift on HV side MOSFETs, so the LV side MOSFETS switches at the same moments, as Diodes, to compensate for the voltage drop on the output

Active switching (MOSFETs) on the LV results in a lower output voltage, than is defined by the CLLC transfer function. The output voltage is only correct when conducting passively (Diodes).

Created CLLC_Plecs.slx model to confirm H_abs transfer function value in the resonance point fr1, there it gives the correct simulation result. As soon as I move a small delta out of the resonance point, the output voltage approaches zero.