Language Packs are expected to be installed on the image first, before any monthly update is applied.
If you install them in the wrong order or after the system is live, Windows Update will ask you to re-install the last CU and reboot.
There's no problem in doing this. But if you have removed components, then re-installing the CU might restore some removals. To avoid this situation, always follow this correct order:
1. Load clean ISO. Apply Language Packs to image.
2. Apply updates to image.
3. Remove components.