An AI literally cannot embody pain - it has no nervous system and no pain receptors. So AI is excluded from understanding it in that way by definition. It has no sensory perception of any kind so cannot have the kind of embodied experience. Heck it doesn't even have a body with which to embody anything. This is obviously unsatisfactory because it seems just a logical/rhetorical trick.
It's also no different from the concept of a person with no visual apparatus (mentioned in another comment thread) and whether they have thought about light and colour and so on. The fact that they are physically unable to have the same kind of experience of these things as someone else doesn't preclude them from having thoughts and experiences that are within the domain of their perception.
An LLM is even more limited than an AI generally because it is literally a model of language. I don't personally think that any LLM could conceivably have a theory of mind, but arguing that it cannot have a theory of mind simply because of things that are exogenous to language by definition seems arbitrary.
That pain is what knowing something means.
Philosophically we're talking about embodied qualia, which is how humans experience objects and more basic sensations.
Language happens later - much later.
The defining property of a bag isn't that you can put things in it. Like language that comes later. The defining properties are how it feels when you hold it, when you open it, the differences in sensation between empty/partially empty/full. And so on.
An LLM has no embodied experience, so it has no idea what a bag feels like as a set of physical sensations and directly perceived relationships.
Failure to understand embodiment has done more to hold back AI than any other philosophical error. Researchers have assumed - wrongly - that you can define an object by its visual properties and its linguistic associations.
That's simply not how it works for humans. We get there after a while, but we start from something far more visceral - so much so that many fundamental linguistic abstractions are metaphors based on the simplest and most common qualia.