When you have an excess contribution that is not due to the Roth IRA contribution being excess because of your MAGI for the purpose being too high, which account of these accounts you request the return of contribution be made from doesn't matter with regard to correcting the excess. Although the excess is deemed to be in the Roth IRA, the return of contribution does not have to be from the account were the excess is deemed to be. Reducing the amount of the traditional IRA contribution in this case will still reduce the amount of excess that is deemed to be in the Roth IRA. Of course if obtaining a return of all of one of these contributions does not fully resolve the excess, some amount of contribution will need to be returned from the other account.
(If the excess is due to exceeding the permissible Roth IRA contribution alone, that excess would need to be returned or recharacterized from the Roth IRA.)
And just to be clear, a return of contribution before the due date of the tax return, including extensions, is not an ordinary distribution. A return of contribution before the due date must be explicitly requested.
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