Some people wonder why Apple/Safari/WebKit folks often refer to “Web Apps”, “Home Screen Web Apps”, “Installed Web Apps” or similar terms, instead of “Progressive Web Apps” or PWAs. There’s a couple of reasons:
1. We like to reflect language that appears in the UI when possible.
2. When we intend to refer to installed web apps, the term “PWA” is ambiguous. Sometimes it refers to web apps that _can_ be installed, other times web apps that _have_ been installed. When we’re talking about different capabilities or extra behavior, we generally only mean web apps that have actually been installed, so we try to be more specific.
3. PWA in reference to a suite of technologies is amorphous and has no clear referent. Some technologies are almost always considered part of the core PWA set: Service Workers, Web Manifest, Notifications API, Push API (and related protocols). But other things may be considered PWA, Fugu, or just normal web technologies, depending on the day of the week. We don’t find such an amorphous grouping to be a useful way to think about web technologies.
We’re not mad at other people using the term and will use it when helpful, but this is why we usually use different terminology depending on context.
Contrast Web Components: this really is a clear and well defined cluster. There’s no debate or fuzziness as to whether specific specs are part of Web Components or not.
@othermaciej @phae, who came up with the name, doesn't disagree https://fberriman.com/2017/06/26/naming-progressive-web-apps/