React was open sourced in 2013. Service workers, which I consider to be essential to what we understand as PWAs, shipped first in Chrome in 2015, Safari in 2018.
I completely understand the confusion, but "Progressive Web App" or PWA[1], coined by Alex Russell and Frances Berriman[2], has become a specific term for websites that work normally on a pc but can also take advantage of things like push notifications and be installed on the home screen of a phone. You can see a measurable uptick on Google Trends after this blogpost [3].