modifyHeaders Safari Extension

I want to execute the modifyHeaders method using a Safari extension. However, it doesn't work when I execute it in Safari. It works in Chrome. Why is that? I used this document as reference:

Part of manifest.json

"declarative_net_request": {
        "rule_resources": [{
            "id": "ruleset",
            "enabled": true,
            "path": "rules.json"
        }]
    },

    "host_permissions": [ "<all_urls>" ],
    "permissions": [
        "declarativeNetRequestWithHostAccess"
    ]

rules.json

[
    {
      "id": 1,
      "priority": 1,
      "action": {
        "type": "modifyHeaders",
        "responseHeaders": [
          {
            "header": "Content-Disposition",
            "operation": "remove"
          }
        ]
      },
      "condition": {
        "regexFilter": ".*",
        "resourceTypes": [
          "main_frame",
          "sub_frame"
        ]
      }
    }
]

[https://developer.apple.com/documentation/safariservices/safari_web_extensions/blocking_content_with_your_safari_web_extension]