Float in a variant field of TSQLRecord becomes string when got back from DB

TestFloatInVariant.dpr

program TestFloatInVariant;

{$APPTYPE CONSOLE}

uses
  FastMM4,
  SysUtils,
  Variants,
  SynCommons,
  SynLog,
  SynTests,
  SynSQLite3,
  SynSQLite3Static,
  mORMot,
  mORMotSQLite3;

type
{$M+}

  TSQLSpeed = class(TSQLRecord)
  private
    FPlainObj: Variant;
  public
    constructor Create; override;
  published
    property PlainObj: Variant read FPlainObj write FPlainObj;
  end;

  TSpeed = class
  private
    FVal: Double;
  published
    property Val: Double read FVal write FVal;
  end;

constructor TSQLSpeed.Create;
begin
  inherited Create;
  TDocVariant.New(FPlainObj);
end;

var
  Model: TSQLModel;
  Rest: TSQLRest;
  SQLiteDBPath: string;
  SqlS: TSQLSpeed;
  S: TSpeed;
  ID: TID;
begin
  SQLiteDBPath := IncludeTrailingPathDelimiter(ExtractFilePath(ParamStr(0))) + SQLiteDBName;
  Model := TSQLModel.Create([TSQLSpeed]);
  Rest := TSQLRestClientDB.Create(Model, nil, SQLiteDBPath, TSQLRestServerDB, False);
  TSQLRestClientDB(Rest).Server.DB.Synchronous := smFull;
  TSQLRestClientDB(Rest).Server.DB.LockingMode := lmExclusive;
  TSQLRestClientDB(Rest).Server.CreateMissingTables;

  S := TSpeed.Create;
  S.Val := 1234.567890;

  SqlS := TSQLSpeed.Create;

  Writeln(VarType(SqlS.PlainObj));     // 271

  SqlS.PlainObj := ObjectToJSON(S);

  Writeln(VarType(SqlS.PlainObj));     // 256
  Writeln(SqlS.PlainObj);              // {"Val":1234.56789}
  Writeln;

  ID := Rest.Add(SqlS, True);
  SqlS.Free;
  S.Free;

  SqlS := TSQLSpeed.Create(Rest, ID);

  Writeln(VarType(SqlS.PlainObj));     // 271
  Writeln(SqlS.PlainObj);              // {"Val":"1234.56789"}
  Writeln;

  S := TSpeed.Create;
  ObjectLoadJSON(S, VariantToUTF8(SqlS.PlainObj));
  Writeln(S.Val);                      // 0.00000000000000E+0000

  Rest.Free;
  Model.Free;

end.