Trite remark. The author was referring to behaviour that has nothing to do with “how the web has become.”

It is specifically to do with behaviour that is enabled by using shared resources (like IndexedDB across multiple tabs), which is not simple HTML.

To do something similar over the network, you have until the next frame deadline. That’s 8-16ms. RTT. So 4ms out and back, with 0ms budget for processing. Good luck!