“PWA” is a bit of a nebulous concept, but it basically grew out of this blog post by Alex Russell, who was working at Google at the time:

https://infrequently.org/2015/06/progressive-apps-escaping-t...

When Apple launched the iPhone, Steve Jobs told people that if they wanted to build apps for the iPhone, they should build them as web apps. This wasn’t specifically about PWAs, just web apps in general. Users demanded native apps, so Apple launched the iPhoneOS SDK and App Store the next year.