On one end, you could serve all of your js bundled with browserify on the first page load, which, for SPA's will frequently block rendering until the entire bundle is downloaded, parsed, and executed. If your bundle is small, who cares? Once your app grows to a large enough size, that initial delay might no longer be worth it.

On the other end, you could serve almost no assets with the initial page load, and request what you need when you need it. Your initial render will be blazingly fast but any first interaction might be slowed by the latency involved in going to get the relevant assets needed to execute the interaction.

Somewhere in the middle you may find a solution involving sending half of your assets initially and requesting the other half when you need them.

It's not helpful to write off various methods of asset loading because of assumptions about latency, bundle size, or DOMContentLoaded event delay. The important part of this article is that it speaks to the various approaches to this problem. I'm guessing the author took the time to weigh the pros and cons of these approaches, chose this one which particularly works for him, and wrote about it to share his findings.

This isn't a trivial problem with one solution. Dig into the performance of your apps while wearing multiple hats and take what works best for your situation ;)