Any linearity (or at least partial ordering) of intelligence comes from time and causality, not language - in fact the linearity of language is a limitation human cognition struggles to fight against.
I think this is where "chimpanzees are intelligent" comes to the rescue - AI has a nasty habit of focusing too much on humans. It is vacuous to think that chimpanzee intelligence can be reduced to a linear sequence of oohs-and-aahs, although I suspect a transformer trained on thousands of hours of chimp vocalizations could keep a real chimp busy for a long time. Ape cognition is much deeper and more mysterious: imperfect "axioms" and "algorithms" about space, time, numbers, object-ness, identifying other intelligences, etc, seem to be somehow built-in, and all apes seem to share deep cognitive tools like self-reflection, estimating the cognitive complexity of a task, robust quantitative reasoning, and so on. Nor does it really make sense to hand-wave about "evolutionary training data" - there are stark micro- and macro-architectural differences between primate brains and squirrel brains. Not to mention that all species have the exact same amount of data - if it was just about millions of years, why are bees and octopi uniquely intelligent among invertebrates? Why aren't there any chimpanzee-level squirrels? Rather than twisting into knots about "high quality evolutionary data," it makes a lot more sense to point towards evolution pressuring the development of different brain architectures with stronger cognitive abilities. (Especially considering how rapidly modern human intelligence seems to evolved - much more easily explained by sudden favorable mutations vs stumbling into an East African data treasure trove.)
Human intelligence uses these "algorithms" + the more modern tool of language to reason about the world. I believe any AI system which starts with language and sensory input[1], then hopes to get causality/etc via Big Data is doomed to failure: it might be an exceptionally useful text generator/processor but there will be infinite families of text-based problems that toddlers can solve but the AI cannot.
[1] I also think sight-without-touch is doomed to failure, especially with video generation, but that's a different discussion. And AIs can somewhat cheat "touch" if they train extensively on a good video game engine (I see RDR2 is used a lot).