Why Google Slides not Autofit text in placeholders?

I have a simple slide where the placeholders are all set in: Shrink text on overflow.

Despite this, the text is not reduced and through the Api I discover that the Autofit is not set. In setting it, however, I get the following error: Autofit types other than NONE are not supported

Code of requests:

requests = [
            {
        "updateShapeProperties": {
            "objectId": 'gda51db96da_1_5',
            "shapeProperties": {
                "autofit": {
                 "autofitType": 'TEXT_AUTOFIT'
                }
             },
        "fields": "autofit.autofitType"
        }

            }
        ]