The app in question ("Navalny app") has a blog and voting recommendations. You can distribute information with app updates or use push notifications to transmit data (for example, new API server IP address and public key).
For example, when government tried to block Telegram, it used push notifications to send addresses of new (not yet blocked) servers to the app (of course, you can send different addresses to different devices). It helped Telegram to evade blocking and it worked.
As I understand, you cannot do it with PWA, especially if the browser doesn't encrypt DNS requests.
So with native apps the only way to block them is either block App Store completely or push on Apple to remove the app.
If the browser supports encrypted DNS and hiding SNI (which needs TLS >= 1.3) then there are chances to evade blocking with PWA. But as I understand, Safari doesn't use encrypted DNS by default (I wonder why).
The government might have only pretended that it really tried to block Telegram. The app was never removed from stores, and since both G and A did comply with such requests before abd after, I suspect that such request was never sent in the first place.
For example, when government tried to block Telegram, it used push notifications to send addresses of new (not yet blocked) servers to the app (of course, you can send different addresses to different devices). It helped Telegram to evade blocking and it worked.
As I understand, you cannot do it with PWA, especially if the browser doesn't encrypt DNS requests.
So with native apps the only way to block them is either block App Store completely or push on Apple to remove the app.
If the browser supports encrypted DNS and hiding SNI (which needs TLS >= 1.3) then there are chances to evade blocking with PWA. But as I understand, Safari doesn't use encrypted DNS by default (I wonder why).