Why wouldn't you want an LLM for a language learning tool? Language is one of things I would trust an LLM completely on. Have you ever seen ChatGPT make an English mistake?
Grammarly is all in on AI and recently started recommended splitting "wasn't" and added the contraction to the word it modified. Example: "truly wasn't" becomes "was trulyn't"
Gemini: "Was trulyn't" is a contraction that follows the rules of forming contractions, but it is not a widely used or accepted form in standard English. It is considered grammatically correct in a technical sense, but it's not common usage and can sound awkward or incorrect to native speakers.