Pure js without typescript also has "types". Typescript doesn't give you nominal types either. It's only structural. So when you say that you "know it's already been processed", you just have a mental type of "Parsed" vs "Raw". With a type system, it's like you have a partner dedicated to tracking that. But without that, it doesn't mean you aren't doing any parsing or type tracking of your own.

I don't think that's what people are talking about when they say types. They're talking about TypeScript types, not mental models of object structure.