It strikes me as odd that Project Zero is listed as having discovered this in mid-2017. It seems like this vulnerability and the browser mitigations being considered only just now were discussed quite some time ago:
This comment was on April 7, 2017: https://news.ycombinator.com/item?id=14057091
And this one from 2015? https://github.com/tc39/ecmascript_sharedmem/issues/1