alt Hacker NewsResearch on LLMs suggest that's probably not the case. See the work on reasoning in latent space, and on shared concepts between languages being represented independently of the individual language.
Of course one might argue that even if LLMs are capable of ideation and conceptualisation without natural language, doesn't mean humans are.
But the fact that up to 50% of people have no inner monologue seems to refute that.
Humans can't share ideas directly, they pass through language. Some idea is created at the other end, nominally the same one, but there's no reason to suppose a universal internal format. Even translating between human languages loses details, where words in one language map imperfectly to words in another. Moving ideas directly from one brain to another probably can't happen. So the statement in language doesn't map very well to the idea (whichever person's version of the idea). And at some point before the idea is formed there has to be some sort of proto-idea or potential, with less definite boundaries. So "there is no proper idea" sounds right to me. There's something idiosyncratic, not the formal idea that's frozen when put into words.