Open Web Advocacy has a post about the degree of regulatory and activist pressure was brought to bear to make this happen.
A thing I'm curious about is on what timeframe, if at all, third party browsers will wind up being allowed to do home screen PWAs. It does seem somewhat impractical to spec, write API for, and implement such a feature before any third party browsers even exist, but one thing Apple is right about is allowing Safari to make home screen PWAs but not alternate browsers is not creating a level playing field.
