I wish there was a way to disable this functionality.
It’s even worse when combined with lazy scroll-based loading: now you’re guaranteeing that I’ll see the unpleasant version briefly (especially in Australia, I imagine, where there’s generally higher latency on such requests than in the USA—but I haven’t tried Medium or similar sites from the USA, so I’m not sure if it’s as unpleasant there).
It’s worst of all when combined with lazy scroll-based loading and an unreliable internet connection: I load pages in places where I know I have an internet connection, and then read them in places where an internet connection is unavailable. With lazy loading of these things, I can no longer be confident that it’s actually loaded everything I need. Same deal with Medium’s blocked iframes for things like CodePen—that just means that the iframe is not loaded when I need it to be.
I want less magic, not more, because we’ve proven as an industry that we’re not responsible with magic, and always manage to make a mess with it.
Edit: Maybe they're not sneakers, but they're shoes. I just wear loafers, I really have no idea what any shoe types are called.