Indexing script with parameters into percolation field breaks in 8.5

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1

When indexing into a percolation field on a document, we submit something like:

{
    "bool": {
        "filter": [
            {
                "script": {
                    "script": {
                        "source": "blah blah params['points']",
                        "params": {
                            "points": [...]
                        }
                    }
                }
            }
        ],
        ...
    }
}

This works fine on anything before 8.5, but on 8.5 and after it raises this error:

{
    "type": "mapper_parsing_exception",
    "reason": "failed to parse",
    "caused_by": {
        "type": "x_content_parse_exception",
        "reason": "[1:344] [bool] failed to parse field [filter]",
        "caused_by": {
            "type": "x_content_parse_exception",
            "reason": "[1:344] [script] failed to parse field [params]",
            "caused_by": {
                "type": "unsupported_operation_exception",
                "reason": null
            }
        }
    }
}

When using the same query to filter the documents instead of attempting to index it into a percolation field, it works fine on 8.5 also.

From what I can see, nothing relevant changed in the documentation for scripts/percolation between these versions, and there is nothing in the release notes.

Thank you