Hi all, I am feeling stupid. Please could someone tell me why the following search returns more than 4000 results?

var searchObj = search.create({
            type: search.Type.ITEM,
            columns: ['itemid', 'isinactive'],
            filters: [
                search.createFilter({
                    name: 'internalid',
                    operator: search.Operator.ANYOF,
                    values: ['this_is_not_an_internal_id_value']
                })
            ],
        });

I think it should return no results since this_is_not_an_internal_id_value is not an internal id value.