Installing Kali on USB stick 8 GB ... no more space left on device

I find really interesting that on the official page it is suggested to use at least a 4 GB USB stick, because after installing Kali on a 8GB USB stick and updating it, and have received a "no more space left on device" error during the update, there is almost no more free space left. I think that this information should be changed in the docs, otherwise other people will waste their time to install Kali on a small USB stick to just discover that the system after the installation is almost unusable, because it is impossible to install any other mid-sized application and future updates can also be very difficult with the few free space left.

http://i.imgur.com/DxzudhA.png

You can install Kali on a 4gb USB as long as that is all you are installing. All docs say that. I have a USB distro from 1.5 years ago with updates every week and as long as you are running the correct code to remove old data, you should be fine.