If the bear is attacking you, you may get one chance to do what you can in a second's time. If you haven't done by then, you are not going to get to do it. There will not be time to think through options. If you don't have it ready, it will not be used.
I think generally you're right but last fall here in Bozeman a young man was attacked by a Grizz. Kid barely saw the bear before it was on him. It charged and knocked him flying into a tree, and as he was under the bear he managed to retrieve his bear spray from his backpack
on his back (!)and drive off the bear! Man, hope the kid bought a lottery ticket on the way home.
I think the most important thing is to not assume you're dead until you actually are! Keep doing everything you can til the bear digests you!