... or at least as how I expected it to

Clicking on an EuiFilterSelectItem does not change it's checked state.

Issue #3735 makes it sounds like we are supposed to use EuiFilterGroup in conjunction with something else like EuiSelectable, but I can't find any examples of this. Have I missed something?

Also, this sentence is repeated

Add the prop withNext to remove the border between it and the next EuiFilterButton to visually group similar or opposite style filters.