This is not the full picture here. PWA are just a thin shell to do one thing, no more than that. Their "small" size all depends on what you are comparing them against (I think this is wrong). Android had "instant-apps" with a similar technique, and they were/are too limited. They can be built by web developers, it is a web page loaded as an application, scripted, and running in a browser within an application. If you think about it you are deploying a browser, with pre-loaded webpage. WebOS did this in 2010 for apps (not great for games, sensor processing, bluetooth, ...). Know when to use them, but for the most part don't make them.