Why do Vector property need to be marked Searchable

In my ontology I have a Vector property that is used for KNN search. I don’t want users to be able to run filters, sorts or aggregations on the property. Additionally I don’t want to incur the cost of indexing this property if it can be avoided (ie I only want to index it for the KNN search).

However to refer to the property in Typescript Functions the property seems to need to be marked ‘Searchable’ (without this my Functions build fails).

When a Vector, that is used with an embedding model, is added to the ontology, why do we need to mark it as ‘Searchable’?