Leakage current comes in many different frequency bands. Different parts of the VFD produce leakage currents of different frequencies. You can see below the main sources of leakage currents:

In theory, the aggregate of all earth leakage currents should add up and increase the total leakage current (1+2+3+4). However, from practical experience we discover that adding an EMC filter to a frequency converter (VFD) that doesn’t have one, can sometimes lower the total leakage current. That is because the capacitors of the EMC filter can absorb the high-frequency leakage (3+4) that is generated by the switching frequency of the VFD output.

If you have a situation in which your B-Type RCD (Residual Current Device) never trips when it is in standby (Stop mode) and only trips when running the motor, then one solution to that could be to install an EMC filter. However, it is worth testing such a solution beforehand because depending on the capacitance of the EMC filter, the low frequency leakage current (1) could be increased to the point at which it trips the RCD immediately at power-up.

In short, adding EMC filter will increase the total leakage current when the VFD is powered up and in standby but it can help decrease the total leakage current when the VFD output is active.