This behavior is the result of the layer used as the application's locator or search source having a full-text index on the field used within the search. Removing the index will revert the query back to a "where" clause. For more information, please see https://doc.arcgis.com/en/arcgis-online/manage-data/manage-hosted-feature-layers.htm#ESRI_SECTION1_0D8D9E34EAB642228377FAAE466A826C