Good question and I can see how this would be confusing!
Translated content isn’t indexed for search, so keyword search only matches the original language. What you’re seeing here on Meta is most likely AI semantic search (ai_embeddings_semantic_quick_search_enabled).
When keyword search returns few results semantic search kicks in to add matches by meaning, which works across languages without translating anything. The result then shows the title in your language because we display the translated title in search results.