Every gift can be refused or discarded. That's not the same as "strings attached."
i) What if an accident victim is wheeled into the ER with severe internal injuries. He needs a liver transplant. But he's unconscious. He can't consent to the procedure. His wife signs the consent form on his behalf.
When he wakes up after surgery, can he still refuse or discard the donated liver? Will he cut it out?
iii) This also suffers from a particular image of what constitutes a "gift," like a Christmas present you can return to the store.
Even then, stores refuse to refund a used gift.
But in Calvinism, saving grace isn't that kind of gift. Saving grace is like a cure for mental illness. Something that's internalized. It changes you. Becomes a part of who you are. Restores your mental health.
It's too late to refuse. And you can no more discard it than you can discard yourself.
Of course, Olson rejects the Reformed doctrine of grace. My immediate point is that his objection is meaningless in reference to Calvinism.