You "actually understand" if in saying words, w, about a situation, s, the reason, r, you say those words counts as as an understanding of s.
So if you're asked, "what is the weather today?" and a system replies, "its sunny" -- it only understands if the reason it replied was because its saying "sunny" had come about because it understands sunny sitations; and therefore has a justfiied reason on this occasion to say that this occasion is sunny.
If I ask a NN trained on a trillion documents, "do you like what I'm wearing?" it cannot answer. It can say the words, "yes I do!" but it cannot have a reason to say those words. It's just a "weighted average retrievla across a compressed dataset of a trillion documetns".
The question isnt "on average, what -- historically -- would a generic person reply to the question: do you like what i'm wearing?"
The question is if the systems likes what I'm wearing. Its replies are only "actual replies" if it can see what i'm wearing, has experiences/preferences for taste, has some aesthetic judgement, has a disposition to like/dislike -- etc.
No ML system on the planet, in this sense, has any understanding whatsoever. Interpolation over historical data is just a means of compressing history into parameters, ie., its a compressed lookup table. That isn't ever a /reason/, exactly, if a person simply used such a table -- they wouldnt mean what they said