custom managed record and memory leak - delphi

Question

Using Delphi 10.4.1 I tried Custom Managed record management to initialize a record but still get memory leaks.
unit Unit3;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
System.Classes, System.IOUtils, System.DateUtils, System.Character,
Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.ExtCtrls;
type
TForm3 = class(TForm)
Button1: TButton;
RadioGroup1: TRadioGroup;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form3: TForm3;
type
TMyRec = record
DateTime: TDateTime;
v, size: integer;
str: string;
class operator Initialize (out Dest: TMyRec);
end;
TMyREcHolder = class
data: TMyRec;
constructor Create(const e: TMyRec);
end;
TMyList = class(TList)
procedure Clear; override;
end;
implementation
{$R *.dfm}
class operator TmyRec.Initialize (out Dest: TMyRec);
begin
Dest.str := '';
end;
{ TMyREcHolder }
constructor TMyREcHolder.Create(const e: TMyRec);
begin
inherited Create;
data := e;
end;
{ TMyList }
procedure TMyList.Clear;
var
i: integer;
begin
for i := 0 to Count - 1 do
TMyREcHolder(Items[i]).Free;
inherited Clear;
end;
procedure TForm3.Button1Click(Sender: TObject);
var
lst: TMyList;
i: integer;
rec: TMyRec;
FI: TSearchrec;
begin
Initialize(rec);
lst := TMyList.Create;
try
if FindFirst(TPath.Combine('C:\temp', '*.txt'), faAnyFile, FI) = 0 then
begin
repeat
if (FI.FindData.dwFileAttributes and faDirectory = 0) and
(FI.FindData.dwFileAttributes and faArchive = faArchive) then
begin
Application.ProcessMessages;
case RadioGroup1.ItemIndex of
0: Initialize(rec);
1: rec.str := '';
2: fillchar(rec, sizeof(rec), 0);
end;
try
rec.DateTime := FI.TimeStamp;
except
rec.DateTime := EncodeDateDay(1970, 1);
end;
rec.size := FI.size;
rec.str := FI.Name;
lst.Add(TMyREcHolder.Create(rec));
end;
until (FindNext(FI) <> 0);
FindClose(FI);
end;
finally
lst.Free;
end;
end;
end.
The radiogroup offers three items, both 1 and 3 leak memory. Can anyone explain why the Initialize one does? I want a reliable way of clearing a record to help me wean myself off a 20 year fillchar habit.