Update ubuntu phone from Nexus 4 directly

Update ubuntu phone from Nexus 4 directly

im using the ubuntu touch/phone on my new nexus 4 (ordered it to try
ubuntu on it). I was asking myself how i can update the phone with daily
builds.
I know about the
http://cdimage.ubuntu.com/ubuntu-touch/daily-preinstalled/ preinstalled
images but also saw that on my phone, if i go to settings/updates/ show me
that there is an update available. If i try this, it says "you can update
from version 0 to version 201..." and its about 250MB of download size,
after a few minutes ubuntu tell me to reboot my phone. If i accept that i
found myself in the bootloader. If i reboot from here the phone is not
updated. If i search again for updates (settings/updates/) the same update
shows up.
Is the build in update function only a dummy? Or am i doing wrong here? Do
i have to choose another option in the bootloader to install the latest
updates?
Or is an update only possible from the shell with the andriod device
bridge (ADB)?