All mega deletes should be authorised. A human person should type in the word "delete" and then only the action should take place. Not doing this is like the decision is taken by VOID created by complex interacting systems.
If GCP is composed of 10-30 services (hypothetically) then keeping 5-10 employees whose job is ensure mega deletes are safe is not too much of a cost.
If GCP is composed of 500 services, then it is all the more important to have humans in the loop so ensure correct behaviour so that complex interacting services don't take a wrong action.