Blog posts in the form of "Here are the technologies making it possible to bring modern native gaming to the web" have been around for a long time, and that's probably the sort of thing they're referring to.

One that comes to mind as particularly memorable is the asm.js Citadel demo (some info here: https://blog.mozilla.org/en/mozilla/mozilla-and-epic-preview...), although there was a similar one a year earlier about UE3 (https://blog.mozilla.org/en/products/firefox/mozilla-is-unlo...).

In 2015, Unity 5 was released with WebGL support. Engine support for having the Web as a target certainly led to a lot of excitement among gamers at the time too.