Is Windows 10 Update Assistant Necessary?

The Windows 10 Update Assistant enables users to upgrade Windows 10 to the latest builds. Thus, you can update Windows to the latest version with that utility without waiting for an automatic update. However, the Update Assistant is hardly essential as the updates will eventually roll out to you without it.

Is it OK to uninstall Windows 10 Update assistant?

So, yes, you are quite right to uninstall Update Assistant in Settings > Apps > Apps & Features. It is not needed any further, or ever really.

Is it safe to use Windows Update assistant?

It is safe to use Windows Update Assistant to update your version, it will not affect your computer’s working and it is perfectly safe to use it in order to update your system from 1803 to 1809.