TurboTax doesn't really know why you are amending, so it does not add the "Filed pursuant to ..." statement. To include this statement at the top of the amended return you would have to paper-file the amendment after writing the statement at the top of the return yourself. You might instead include the statement in the explanation section of Form 1040-X, but some of the IRA instructions do say that this statement should be present at the top of the form.
