Ideally, to save bandwidth on both sides, the server would only want to serve you the JS and CSS you need. I'm not sure how frequently that optimization is made, however.

Fair point, there could be reasons, and I'd say there's no privacy concerns if that's all they get, but I know it's part of fingerprinting. I said 99% so they don't even need to know that

that's how css gets its media queries, user agents