When having hidden advancements in an advancement tab, the layout gets formed as if those advancements are actually there. Which results in having a weird layout with open gabs where "hidden" advancements will appear when granted/achieved. Because of these open spots, the hidden advancements aren't really hidden anymore. (See attachment)

The borders of the layout also change if there are hidden advancements. For example, when having a hidden advancement above a non-hidden advancement, you are still able to drag the menu to that place where the hidden advancement is, while there is nothing there (yet).