Comment # 7 on bug 1231482 from Fabian Vogt

(In reply to Arvin Schnell from comment #6)
> I have done a test installation and AFAIS the filesystem is labeled
> during the first boot of the system - not during installation. So
> the first snapshot is made before the filesystem is labeled. I think
> that is wrong - the labeling must happen before the snapshot is made.

Yes, which is why this needs to be fixed in the installer.

Kiwi does it properly:
https://github.com/OSInside/kiwi/blob/5416ae8f602fbf0a0466528f9a1be47368b4f67a/kiwi/system/setup.py#L549