If form fields do no mention type, they are by default assumed to be of type text-single.
This causes problem in cases where multiple form field values are included without mentioning type. (https://xmpp.org/extensions/xep-0157.html#example-2).
However, field standardisation for the same xep-0157 (https://xmpp.org/extensions/xep-0157.html#registrar-formtype) suggests that the form field type is list-multi. And so, it is better if the server adds type to the dataform as this saves the client from first checking `FORM_TYPE` and determine form field type as per standardisation .