It's interesting to me that this is almost exactly the flow for installing Firefox on macOS as well, and yet on a Mac it's not used as an opportunity to convert users to Safari (yet?).

macOS requires user explicit user interaction to install and use an app from outside the store (same), and prompts with a system security prompt the first time you do this (same), and if desired this functionality can be turned off at the system (same).

The difference is that the security prompt on macOS makes no mention of browsers, App Store apps being more "trusted" or anything like that.