Retirement tax questions

@DanaB27sorry to bother you again...you stated "For the return of an Roth IRA excess contribution the Form 1099-R should have codes P and J since code P only indicates the removal of an excess deferral. You might want to inform your financial institution."  My financial institution is not fully cooperating and is not sure they need to also use code J.  What happens if I only use code P?

I tried both ways, i.e. only code P and then using code P and J. It didn't seem to affect TT in anyway.  Why is that? I expected to see Form 5329 line 1 and 2 to have something in them when using both codes J and P, no?