GraphQL Tag search using CONTAINS_NOT

Hi folks,

I have a (simplified) query for searching Content Fragments where sometimes I want to exclude certain tags:

query getHelpFaqSearch(
    $value1: String!,
    $operator1: StringOperator = CONTAINS) {
    helpFaqList (
        filter: {
            _tags: {
                _logOp: AND
                _expressions: [ 
                    {
                        value: $value1,
                        _operator: $operator1
                    }
                ]
            }
        }
   ) {
       items {
           question
           answer {
               html
           }
           lastUpdated
           tags
           _path
       }
   }
}

However; if I use the VARs:
{
     "value1": "domain:digital/booking/make",
     "operator1": "CONTAINS_NOT"
}

I get back results like:

...

"tags": [
    "domain:digital/booking/make",
    "domain:digital/booking/connections",
    "domain:digital/travel/day-of-travel",
    "domain:digital/travel/get-ready-to-travel"
],

...

This entry doesn't return:

...

"tags": [
    "domain:digital/booking/make"
],
...

If on the second example I add another tag then that results returns also. So the result is getting hit because of the new tag.

Is there anyway of excluding a CF if a tag exists in both cases?

Thanks,

Graham