Non-native English speakers whose native language doesn't distinguish countable and uncountable nouns is a possibility, but it's still very strange to say "two codes" in those languages, it doesn't have a clear meaning.

Until you see that "code" in ordinary-day language is an ugly word, it's ill-defined, and is used to refer to so many things, but usually with implications of secrecy or espionage. For example, it can refer to the combination of a lock, e.g. a password. It can refer to an encoding scheme or an encoder, e.g. Morse code, Pulse-Code Modulation. It can refer to a codename, e.g. Project X. And most commonly, it refers to an encryption algorithm (or its output), e.g. AES (or ciphertext), or a sentence of something written in a programming language, e.g. "one-liner".

And most people who don't have an engineering background usually don't realize those are not the same thing, they think a telegram in Morse code, a ASCII-encoded string, the combination of their lock, an encryption algorithm, or a line of code in programming language are the same thing, they just picture it as a number (well, they are numbers, all information is numbers, but their visual representations and purposes are very different) - when you have this mentality, "a code" or "two codes" makes sense.

Probably because a lot of people on the internet are not native English speakers, and so struggle to see the difference between "cat" and "code".

I think it's British or European usage.