I generate a super flat world but this is what happened

Steps to reproduce:

1.-Generate a superflat world on creative (I don't know if this works in survival)
2.- Close Minecraft's app
3.- Enter in Minecraft and select the world that you generate previously (Note: this step must do before that Minecraft log in on xbox live)
4.- It will show a window that say us "Wait a few Minutes" (or something like that)
5.- If you press to enter in this world that you generate, the game won't let you in
6.- Close Minecraft's app
7.- Open Minecraft's app
8.- Enter to the world generate
If you did correctly you can see how all the chunks tjat you was charging doesn't affect, but the chunks that you wasn't charging, will generate world like a normal generation