The concern here seems to be that the credit risk on the underlying borrowers is being transferred to banks through the loans made by the banks to the private credit firms. But the banks' lending to the private credit firms is subject to the same regulations and constraints as their lending to other borrowers (the same regulations and constraints that led them not to lend to the underlying borrowers in the first place). When banks lend to private credit funds/firms, it tends to be through senior, secured loans which will be less risky than the underlying loans.