You didn't answer the question if it's ok in the scenario I've explained.
It's not the initial loading screen, but a phase in the app that takes some time to perform.
Is it ok in this scenario, or not?
Examples of such scenarios:
1. If it's a game, it's a loading screen of the game.
2. If it's a video editing/conversion app, it's the process of exporting the video.
3. If it's a contacts-related app, it's some large operation on the contacts (merging, syncing, maybe something with cloud...)
4. If it's a backup app, it's the backup operation.
etc...