interesting work, will need to dedicate time to read this. From what I understand, this is for WebKit only? So this does not apply to Chrome based rendering. And this doesn't seem officially supported by Apple, so this is more of an academic curiosity rather than something that we could practically expect to see in Safari?
The article links to this bug report containing a patch of the ongoing work in the WebKit engine
It's part of WebKit itself, so shared by Safari, yes... Igalia is the #2 contributor to WebKit behind Apple with ~16% of all commits (we maintain a few official ports, including the one used for embedded devices, WPE WebKit). Sony are also significant contributors to WebKit. So, it's not an academic exercise, no. Apple WebKit engineers have been quite supportive..