loading="lazy" is for images that are NOT embedded in the same file. So we either have entire site in a single HTML file or we have scalability for large stes. There's no solution that gives us both.
It depends on what your goal is. If you just want to make a single request to the web server, than loading="lazy" will not work as you said. (Technically speaking, TCP is sending multiple packages anyway resulting in higher latency, so not sure if that is a great goal.)
But if you just want to be able to save the entire website with Ctrl + S, then it works fine.
As an aside, loading="lazy" is the way in which images are embedded in the website from TFA https://i.imgur.com/wIkaE5g.png which was the reason why I mentioned it, although it certainly does not fit all possible use cases.
