I would suggest don't ruin his case with a study permit application, to keep him on a super visa, the only disadvantage is you will have to pay for his medical expenses.
So the conditions of change required are that you should be enrolled at the old DLI and actively studying while you change your DLI. If you did not enroll to this old school at all then that breaches the conditions...
What made you show them the old one and not the new one when you are arguing that you sent them new LOA and got approval after the webform? you knowingly deceived them and now want us to tell you everything is okay?
They don't need to confirm the change, the onus lies on you to abide by the conditions set out for a study permit status to stay valid. If the conditions are breached then your PGWP application will be refused.