It is not that the IRS will not start processing returns with the additional child tax credit; it is that they will not issue refunds before mid-February if you are getting EIC or additional child credit. Not the same thing. Even if they have processed your return they hold the refund.
The loan information does not make any reference to holding the loans if you are getting child credits.
So be on the lookout after Jan. 27 when your return could be accepted. The loan could be released shortly after that.