Webhook "Unsupported field". Field exists and has correct name.

I have added the following field to Leads (and Accounts, Contacts. Opportunities on conversion):

Field Label: requestRef
It is marked as an external field, at the organization level.
It is marked as 'show' - it is visible.

I am able to set it with my api call, and see it in the object view.

I can see it in my call to get meta data for the Object (See below).

When I attempt to reference the field in the WebHook, I get the dreaded Webhook "Unsupported field" error.

Call to "/crm/v3/settings/fields?module=Accounts"

Relevant snippet:

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        {
            "system_mandatory": false,
            "webhook": true,
            "virtual_field": false,
            "json_type": "string",
            "crypt": null,
            "field_label": "requestRef",
            "tooltip": null,
            "created_source": "default",
            "type": "used",
            "field_read_only": false,
            "display_label": "requestRef",
            "display_type": -1,
            "ui_type": 1,
            "modified_time": "2023-03-20T17:55:04-04:00",
            "read_only": false,
            "association_details": null,
            "email_parser": {
                "fields_update_supported": true,
                "record_operations_supported": true
            },
            "businesscard_supported": false,
            "multi_module_lookup": {},
            "currency": {},
            "id": "4994356000001777045",
            "custom_field": true,
            "lookup": {},
            "created_time": "2023-03-20T17:55:04-04:00",
            "filterable": true,
            "visible": true,
            "profiles": [
                {
                    "permission_type": "read_write",
                    "name": "Administrator",
                    "id": "4994356000001037015"
                },
                {
                    "permission_type": "read_write",
                    "name": "Standard",
                    "id": "4994356000001037018"
                }
            ],
            "length": 255,
            "view_type": {
                "view": true,
                "edit": true,
                "quick_create": false,
                "create": true
            },
            "display_field": false,
            "pick_list_values_sorted_lexically": false,
            "sortable": true,
            "subform": null,
            "separator": false,
            "searchable": true,
            "global_picklist": null,
            "external": {
                "show": true,
                "type": "org"
            },
            "api_name": "requestRef",
            "unique": {},
            "enable_colour_code": false,
            "history_tracking": null,
            "data_type": "text",
            "formula": {},
            "decimal_place": null,
            "mass_update": false,
            "multiselectlookup": {},
            "pick_list_values": [],
            "auto_number": {}
        },

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