It is far from clear that this presumption holds.
Ingesting more text than a human could read in several lifetimes produces the ability to interpolate answers to a surprisingly large range of questions. This is not intuitive to humans, because we've never met anybody who could possibly read this much raw text, so we mistake this level of interpolation for reasoning since we've never met anybody who could possibly memorize-and-interpolate so much. The only thing we've ever seen that can answer questions like this is a human using reasoning capabilities, so we assume that's what this thing on the other side of the screen must be doing. Like chimpanzees mistaking their own reflection in a mirror for another ape.
This is the other "bitter lesson" of ML.
But if you spend enough time playing with these models you start to figure out what questions to ask to make them look foolish. And that is totally fair game for the Turing Test. Remember, there is no time limit on the Turing Test. However there is a strict requirement that the machine under test cannot be serviced, modified, or updated while the test is underway -- and because of this, nothing that OpenAI has produced is capable of even taking the test. We know that OpenAI tweaks and tunes their models whenever they please, as many times a day as they like, and that they use discussions here on HN to feed that process. So stick to the models you can download.
It's uncontroversial to say that this sort of "massive interpolation using superhuman text ingestion" is exactly how modern machine translation models work, and they work extremely well. LLMs were created by taking a machine translation model, throwing away half of it, and then fiddling with the leftovers.