Well he would not be liable to criminal prosecution, but that says nothing of whether the loans have to be forgiven upon his declaration.
The immunity just stops him from facing personal legal consequences and only after SCOTUS confirms any crimes were committed during an official act. How do they test for that? They haven’t said and will make up reasons to help/hurt whoever they want on a case by case basis.
Are there laws Biden could break that would force loan forgiveness, and would the current supreme court side with Biden? Seems like no in both cases aside from more Seal Team Six arguments resulting in a new set of SCOTUS judges ruling on such orders. Biden ain’t the guy to make that happen.