The level isn't frozen before the loading screen ends
As indicated by sounds, or your ability to interact (reported as a separate bug) with the game before the loading screen finally disappears, the game isn't frozen. This is not alright as some process may resume while the player isn't able to play yet.
Why you can't pause-unpause the game though like the user can when he opens the menu?
Honestly it's a bit above my head. But my presumption is that it would affect the process of initializing the level and thus would have the impact I stipulated above.