`ResourceDiff.Get()` doesn't return all the data

SDK version

v2.21.0

Relevant provider source code

&schema.Resource{ // Root resource
	Schema: map[string]*schema.Schema{
		"analysis_definition": {
			Type:     schema.TypeList,
			MaxItems: 1,
			Required: true,
			Elem: &schema.Resource{
				Schema: analysisDefinitionSchema,
			},
		},
	},
	CustomizeDiff: func(ctx context.Context, rd *schema.ResourceDiff, i any) error {
		helper.Logger.Printf("Data: %#v", rd.Get("string"))
		helper.Logger.Printf("Raw: %#v", rd.GetRawConfig())
		return nil
	},
}

Terraform Configuration Files

Some text was replaced but structure is unchanged
Note fields field is a TypeSet, and items is a TypeList

resource "analysis_definitions" "test" {
  analysis_definition {
    name        = "name"
    description = "description"
    model_id    = "d9f4e470-f4ad-456c-8b8e-47577a8212cd"
    node_id     = var.node_id
    inputs {
      type = "STRUCTURE"
      fields {
        name = "example1"
        type = "STRUCTURE"
        fields {
          name = "example2"
          type = "ARRAY"
          items {
            type = "STRUCTURE"
            fields {
              name   = "id"
              type   = "TEXT"
              source = "STATIC"
              value  = "This value doesnt appear!"
            }
          }
        }
      }
    }
  }
}

Debug Output

This is from my Logger.Printf() code. Some text was replaced but structure is unchanged.
https://gist.github.com/N1ark/805c152bc2cea3155189a6dfdf7c411f

Expected Behavior

Although the outputs of Data and Raw are different (one is a map[string]interface{} and the other is a cty.Value, they contain the same data.

Actual Behavior

The Data output seems to be cut - after a certain depth the data output by "Data" isn't present and is instead nil .
Simply search "items":[]interface {}{interface {}(nil)} in the gist to find it.
This data is present in Raw (search for "This value doesnt appear!").

Steps to Reproduce

1. Setup a schema that goes deep enough (mine is done through a recursive function)
2. Write the configuration that goes deep enough
3. Add the given CustomizeDiff snippet
4. terraform init && terraform plan --refresh=false

(Edit: clearer example)

Start with the ResourceDiff.Get and GetRawConfig entry points shown in the CustomizeDiff snippet, then reproduce the nested schema behavior using the provided Terraform configuration. Run terraform init && terraform plan --refresh=false and compare the Data and Raw outputs, including the nested items value; done means ResourceDiff.Get returns the same data present in Raw.