however, at the beginning they tried to force some "progressive" things like responsive design or offline etc. I can understan what they wanted, no need to think of it as self marketing
I like the clarity of websites and we should learn that they can be very powerful: responsive websites, offline functioning websites etc... they can use sooo many web capabilities
I define apps as standalone UX and I use "switch to standalone" instead of "install" (that is what actually happens if someone creates a manifest file which is governed by a draft, not yet standard)
so a website can be implicitly a web app in the sense of rich functionality (responsive, offline) without being used in standalone mode
it will be explicitly a web app if switched to standalone mode from tab mode... this is an important distinction since even if nothing is installed this is a decision from the user to use it from the OS and outside of the browser as a standalone window and on some platforms it may give it some extra rights (local data storage will never be cleared by nice companies like Apple without asking the user, push notifications might be coupled with this decision now or in the future etc)
but I agree, this progressive thing is the past... it actually became the past when browsers gave a shit about what the site ctually functionally can when granting that app button and standalone mode