I mean, I couldn't agree with you more about the asininity of embedding a browser in a 'native' app (for anything other than web browsing). But I use VSCode all day, every day, and subjectively it feels zero-latency on my aging laptop.
On the other hand, this is 2017, and people apparently don't care much about the footprint of their software, as long as it's convenient and it solves their problem. And ultimately that's what counts I guess.