Add a control to a subcomponent inside a custom control

Question

I've created a custom control which is a panel with another panel inside it.

I want the controls added to the outer panel to be actually placed inside the inner panel. TCategoryPanel actually does something similar to this redirecting controls to a surface inside.

Borrowing some code from it I was able to mostly create what I want. Adding a control to the outer panel gets correctly placed inside the inner panel. Also, those controls are correctly saved in the DFM and loaded back in. The problem is the control appears to be outside (a child of the Form) instead of the component in the Structure view:

This doesn't happen in the TCategoryPanel and I can't figure out what is the problem. Everything besides that seems to work. What am I missing?

My component (minimal reproducible example):

unit uTeste;

interface

uses ExtCtrls, Classes, Controls;

type
   TTestePanel = class(TCustomPanel)
   private
      FSurface: TPanel;
      procedure CMControlListChanging(var Message: TCMControlListChanging); message CM_CONTROLLISTCHANGING;
   public
      constructor Create(AOwner: TComponent); override;
      procedure GetChildren(Proc: TGetChildProc; Root: TComponent); override;
   end;

procedure Register;

implementation

uses Graphics;

procedure Register;
begin
   RegisterComponents('Teste', [TTestePanel]);
end;

{ TTestePanel }

constructor TTestePanel.Create(AOwner: TComponent);
begin
   inherited;
   Color := clRed;

   FSurface := TPanel.Create(Self);
   FSurface.AlignWithMargins := True;
   FSurface.Margins.SetBounds(30, 30, 30, 30);
   FSurface.Color  := clGreen;
   FSurface.Parent := Self;
   FSurface.Align  := alClient;
end;

procedure TTestePanel.GetChildren(Proc: TGetChildProc; Root: TComponent);
var
  I: Integer;
  Control: TControl;
begin
  for I := 0 to FSurface.ControlCount - 1 do
  begin
    Control := FSurface.Controls[I];
      Proc(Control);
  end;
end;

procedure TTestePanel.CMControlListChanging(var Message: TCMControlListChanging);
begin
  if Message.Inserting and (Message.ControlListItem^.Parent = Self) and
     (Message.ControlListItem^.Control <> FSurface) then
  begin
    FSurface.InsertControl(Message.ControlListItem^.Control);
    Message.ControlListItem^.Parent := FSurface;
  end
  else
    inherited;
end;

end.