No, it’s not? https://en.wikipedia.org/wiki/Formal_language#Definition

It's an interesting move to point me to a rigorously written English language definition of a formal language to make the argument that humans don't co-opt our natural languages as formal languages when the need arises.

That’s not what “formal language” means. English being used to describe a formal definition doesn’t make it a formal language.

I didn’t say it was a formal language, I said humans co-opt it as one.