Re: 'PWAs need to be fast, engaging, and work offline'
Yes, but presumably you already have Chrome (or Safari, or Edge) installed so you get to reuse that functionality and obviate the need to install a separate app without having to "install" anything.
Compare this approach to various cross platform apps such as Slack or Atom which include a complete (and possibly obsolete) copy of Chrome to use as an application run time.
I'm not saying this is more efficient than a bespoke native application (it's almost certainly not) but the developer overhead is much reduced and may permit apps on more platforms than might otherwise be possible. And the "cost of entry" is practically zero so you don't get bounced to an app store to install an app to get back to the content you were actually interested in (or giving up instead, which is perhaps more likely).
As a real-world example, mobile.twitter.com is a PWA that does practically everything the fat client app does in a fraction of the space. It doesn't necessarily scale to more complex apps (yet) but for a decent subset it's a nice solution.