I have not tried out voyager, but just from looking at it’s GitHub, it’s essentially just a web browser packed in a native app anyways.
Performance shouldn’t really be different from browser app to local app this way unless something is done wrong, or there’s some specific functionality, like async I/o that’s still unsupported.
Notifications are also a thing in web browsers nowadays. Most device features that you can access in a separate app are actually supported by now.
If this design really isn’t asshole design, then why are they still doing it like this? It’s pretty obviously supposed to look like it has more content than it does rn; and even if you do realize what’s going on, this makes it way harder to guess the amount of the contents. A number for gram amount is ok, but your brain really guesses by looking at the content, not the number.