Wow! That took courage to say publicly now with Francis as pope. (Next assignment for the good Prefect: cleaning toilets in Gaza?)
Francis just ignores Mueller. He can say whatever he wants, but it’s like hearing the rain, as far as Francis is concerned.
I don’t think Francis wants to call attention to what Mueller is saying by actively rejecting it, and Francis also doesn’t want to make any statement that will enable people to prove that he is formally a heretic. So he keeps silent and lets his minions do his dirty work.