[Lagerfeldt]

Did you use the provided preset file?

...or did you input the values yourself using the screenshot? I'm wondering if you forgot to set something correctly such as the sidechain.

Did you adjust the frequency in the extended parameters section as explained in the provided guide?

Since the preset will only react to material in a narrow frequency range around the sibilance area, the compressor should not make vocals jump at all - unless you have excessive high frequency material in your recording all the time.

Since this presets does its detection in a narrow frequency area but the actual ducking in broadband (which explains why it can sound so natural) it also means it's not a split band ducker. On a normal vocal recording it will sound very natural when set correctly.