I've always used "proper" sentences for LLMs since day 1. I think I do a good job at not anthropomorphizing them. It's just software. However, that doesn't mean you have to use it in the exact same ways as other software. LLMs are trained on mostly human-made texts, which I imagine are far more rich with proper sentences than Google search queries. I don't doubt that modern models will usually give you at least something sensible no matter the query, but I always assumed that the results would be better if the input was more similar to its training data and was worded in a crystal-clear manner, without trying to get it to fill the blanks. After all, I'm not searching for web pages by listing down some disconnected keywords, I want a specific output that logically follows from my input.