A VCVS and an OPAMP in follower configuration results in an "OPAMP" that better reflects the correct operation in non-linear circuits. In this case, a Schmitt-Trigger circuit is built, and the direct transfer curve accurately reproduces an IRL implementation. The OPAMP in follower configuration brings in the features that are well modeled (saturation voltages, GBW, etc.). Please take into account that the VCVS output corresponds to an OPAMP with no saturation and with ideal input and output resistance, hence should not be used/probed.
