Frequency response of output capacitance in an operational stage
In the real world, adding C3 will make the op-amp run closer to the point of instability and pushing it too far can lead to the opamp becoming an oscillator. Certainly, before oscilation begins, you will see overshoot on the output for a transient input change and therefore purposefully adding capacitance directly to the output of an opamp is generally seen as a bad thing to do.

A lot of opamps will give you some idea (in their respective data sheets) how much capacitance can be tolerated before things get out of control.

Regarding your circuit using the opamp called OPAMP_3T_VIRTUAL, it is unclear why this device is showing the change in response indicated in your diagrams but somewhere, inside the model parameters, there will be the open-loop output resistance value and this is likely to be factored in to any calculation you would wish to make.

As far as I'm concerned, nobody adds capacitance to an op-amp output with the hope of achieving anything useful.