Ok, try this way

the enclosure shields because it is connected to 'protection ground' (e.g. power ground)

This will grab all noise coming from the outside and route it to protection ground.

With your cap some of that noise will pass through the capacitor to signal ground.

So, where the ferrite we both dislike block HF from penetrating from the enclosure to the electronics, your cap block the LF from doing the same while allowing HF penetration.

Schoene Wochenende

Erik