Yes, TLA is a three letter acronym. A four letter acronym, on the other hand, is an ETLA, or “Enhanced Three Letter Acronym”. For advanced cases, you can get an EETLA (or XETLA) for Expanded/Extended Enhanced Three Letter Acronym.

Just so you know.

I suspected as such, that’s why I asked for clarification.

Did you mistype, employ sarcasm, or were you not aware that the genre is named after Metroid, not the other way around? Metroidvania— games employing similar experiences to Metroid and some of the more notable Castlevania games.

Because it became wildly successful. Success brings notice.