GDPR personal_data resource only available on Lithium Studio API Browser

I'm trying to develop a custom endpoint at Lithium Studio,  for exposing GDPR functionality described at GDPR Community API support. The query at API browser looks like this:

SELECT personal_data FROM users WHERE id='SOME_ID'

and it perfectly returns the desired data. Then moving that query to a custom endpoint looks like this:

<#compress>
<#assign error = "" />

<#assign userId = http.request.parameters.name.get("userId", "0") />

<#if (userId != "0")>
  <#attempt>
    <#assign query = "SELECT personal_data FROM users WHERE id='${userId}'"/>
    <#assign resp = restadmin("2.0","/search?q=" + query?url)/>

    ${resp.status?json_string}
      ${apiv2.toJson(resp)}

    <#if (resp.status == "success")>
      <#assign userData = resp.data />
      ${apiv2.toJson(userData.items[0])}
    <#else>
      <#assign error = "there is no user with id " + userId?number?c />
      ${error?json_string}
    </#if>
  <#recover>
    <#assign error = .error />
    ${error?json_string}
  </#attempt>
<#else>
  <#assign error = "userId parameter is required" />
  ${error?json_string}
</#if>
</#compress>

After saving it and trying to access the endpoint at :

https://www.my.community.com/forum/s/TENANT_ID/plugins/custom/company/company/custom.user.personal_data?userId=SOME_ID

The result, returns an empty response, something like this:

{
"status" : "success",
"message" : "",
"http_code" : 200,
"data" : {
"type" : "users",
"list_item_type" : "user",
"size" : 1,
"items" : [ {
"type" : "user",
"personal_data" : {
"type" : "user",
"items" : [ ]
}
} ]
},
"metadata" : { }
}
{
"type" : "user",
"personal_data" : {
"type" : "user",
"items" : [ ]
}
}

Can this be considered a bug?