How can a field's schema type be reused?

Hi everyone, I’m trying to uniquely identify the Request Type field using the /rest/api/latest/field endpoint by going through each field returned and checking the schema.type equals “sd-customerrequesttype”. Note that I’m trying to do this for any Cloud instance.

        "id": "customfield_10300",
        "key": "customfield_10300",
        "name": "Customer Request Type",
        "custom": true,
        "orderable": true,
        "navigable": true,
        "searchable": true,
        "clauseNames": [
            "Customer Request Type"
        "schema": {
            "type": **"sd-customerrequesttype"**,
            "custom": "com.atlassian.servicedesk:vp-origin",
            "customId": 10300

I’ve been informed the schema type can be reused for other fields; how/when would this be done? Can I rely on the schema.type “sd-customerrequesttype” to be unique to this field?

The reason I’m doing all this is to get the name of this field so that it can be used in JQL. This field’s name varies across certain cloud instances as “Request Type” or “Customer Request Type”, so the JQL needed to query using this field can respond with errors. If there’s a clear method of identifying which name the field appears as, please do let me know.