Disabling Maniphest Advance Custom field in certain subtypes

Question
#1

How can I disable a Maniphest advance custom field in a specific subtype? I tried using the https://phabricator.local/config/edit/maniphest.subtypes/but it seems that it cannot change advanced custom field.

Maniphest custom field

final class ManiphestRootCauseCustomField extends ManiphestCustomField

public function getFieldKey() {
    return "maniphest:bug-categorization:root-cause";
}

Subtype implementation

[
  {
    "key": "default",
    "name": "Task",
    "fields": {
      "maniphest:bug-categorization:root-cause": {
        "disabled": true
      }
    }
  },
  {
    "key": "bugid",
    "name": "BugTracker Issue",
    "tag": "BUG"
  }
]