Not true. I saw many install stuff from TestFlight.
Discussion
Btw ever time I try PWA user experience is really bad.
I use a few and the experience is good. I deleted Twitter app and use their PWA, it is much better, the app is horrible.
I also use Cashu mint PWA, I have used ChatGPT as a PWA, all of them are nice and user friendly.
You are right about the URLs, you need to cut&paste them unfortunately.