I don't really buy this post. LLMs are still pretty weak at long contexts and asking them to find some patterns in data usually leads to very superficial results.
In general for chat platforms you're right though, uploading/copy-pasting long documents and asking the LLM to find not one, but multiple needles in a haystack tend to give you really poor results. You need a workflow/process for getting accuracy for those sort of tasks.
And after that? What's next?
Any patterns it identifies could be imaginary, and you don't have any indication of confidence that all relevant trends have been identified. The most valuable patterns are likely going to be the most hidden and easily missed - those are the ones people are paid to find, not just the low hanging fruit that can be identified with basic statistics.
In the same way that asking an LLM to review some code might produce a hundred superficial comments and miss the things that actually matter.