That's kind of a given though. It's a large language model, so of course its "understanding" can only be in terms of language. In a way, words are its only sense (input), and only way to interact with the world (output). The mechanism isn't really important, imo, since we could reduce our own understanding to chemical reactions.
Homo sapiens have many more dimensions of awareness, dozens maybe including sight, hearing, time, pressure, acceleration, etc., and we've been collecting data from them all 24/7 since embryo, plus instinct (pre-baked weights) from millions of years of evolution. We know that people born without a sense, let's say vision cannot conceptualize visually, even when their sight is restored for a time. I remember reading awhile back that a person born blind had their vision fixed, but they didn't know what "pointy" looked like. They couldn't know. Do they have a lower quality understanding of a word?
My point being, I don't think it's fair to objectively compare understanding between a person and a model without a testable definition of that word. Imo, and feel free to disagree, understanding is no different than merely knowing, it's just implied that the knowledge is deeper, across multiple dimensions of awareness, including subconscious awareness of our own hormones.
Been there. Frustrating af