Yes.
This is a common misunderstanding when using EM ports with different (local) grounds. You need to understand that current from the (+) terminal of the EM port will always return to the (-) terminal of that port, and not to any other ground. Or in other words: if you connect an impedance in ADS to ground, that impedance is connected between the (+) terminal and the (-) terminal of that port. Even though it seems that different grounds are connected at schematic level, they are not. They are only connected via ground if that ground path connection physically exists in the EM model (e.g. multiple ports all connected to the same ground in EM model).
So floating or grounded, your active circuit represent an input impedance and that must be connected between the S2P pin 2 and the S2P ground reference => impedance is connected between (+) and (-) of the EM model.