Problem:

Under item.get calls, templateid returns the items's itemid of the template and not the templateid.

On the docs (https://www.zabbix.com/documentation/current/manual/api/reference/item/object):

Hint: Use the hostid property to specify the template that the item belongs to.|

Proof of Concept:

1) item.get and randomly picking an item, I should have 10001 here on templateid of Linux template:

 {
 "itemid": "29167",
 "name": "CPU interrupt time",
 "templateid": "29130"
 },

2) template.get using the itemids of templateid:

{
 "output": ["name", "templateid", "hostid"],
 "itemids": "29130",
 "sortfield": "name"
}

3) And here is it, the hostid 10001 of Linux template:

{
 "jsonrpc": "2.0",
 "result": [
   {
     "itemid": "29130",
     "name": "CPU interrupt time",
     "templateid": "29093",
     "hostid": "10001"
   }
 ],
 "id": 8
}