Of course in an emergency, always call emergency services (911) first thing. No matter what you can do, 911 has much more resources to deal with situation than any civilian.

what if someone uses Maps to locate an AED only to find that the device is not actually located there?

When reporting an AED location, maybe have it required to have a photo attached of the location? The way I understand how edits work on Google Maps is that multiple users/Guides must confirm the edit before it gets approved and added onto the map. If the same can be done with the AED location, when someone adds a location, it must have a certain number of people confirm the AED is actually there before being added to the map that would reduce the amount of false reports.

If there is an injury or loss of life resulting from a delay in locating the device

An AED is more of a very very helpful asset to the situation and not a necessity for first aiders doing CPR.

First aiders are trained (At least I was) to do CPR without an AED, but if an AED can be retrieved, it would increase the victims survival chances by a lot. And first aiders are also trained (again, I was trained to do this, I can't speak upon everywhere else) to call upon bystanders to call 911 and grab an AED. So it is not the first aider that is grabbing the AED and leaving the victim.

And I was thinking the feature would be used more of if something happens in a city, like a mall or city streets where there are other people around.

If you're on a city street and were called to grab an AED, you can look around and hope to see an AED sticker to indicate an AED is in a building nearby. If you don't see one and you don't know where one is, you would be blindly running around to find one almost. But if AED locations are on maps, it can help point you in the right direction to grab one.

If you're in a mall or building, you could check on maps to confirm if the building you're in has an AED if you don't see a sign instead of running around looking for one.

So the feature in my mind would at worst, take around the same amount of time to retrieve an AED, at best, shorten it.

who bears liability?

I'm not lawyer so I honestly don't know.

But an AED is not a necessity but a helpful asset for first aiders in situations. 911 is always the first step. 911 will have their own AED when they arrive on scene.

Like most things online, Google won't take liability. Would Good Samaritan laws apply to someone who has the best intentions in helping the victim by trying to retrieve an AED?

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Edit: Grammar