Okay I’m really glad I asked because I did not know about that feature at all, and it does the job even if in an awkward way (adding a second PWA creates a third page when the second one is hidden). The PWA I was using to test iOS/PWA interactions now shows up in the App Library and Spotlight among the app results.

It’s not great, but as compromises go this one is basically reasonable, though Apple should still just let me dump them straight to the App Library. Thanks!