You can capture the states and feed them to an third party application using state scripts.
There is no interface to capture the progess (%) and this is only printed when doing an update in standalone mode and is not printed when doing an OTA update.
Now on to to the philosophy behind this
Doing A/B style updates, which are also refereed to as “seamless updates” means that you can download the update image in the background without interfering with the currently functionality of the application. For this reason it might not be of interesting to even show anything to the user until it is has downloaded and is ready to be installed (essentially a reboot, because download of the update images means that it is streamed to the inactive partition).
That is why we have not really focused on providing this type of information as this is one of the strengths of A/B update style of updates, that you are able to hide a lot of the progress from the user.
We do have tasks for this though, e.g
But hard to prioritize this over everything else that is more interesting, and we would welcome patches in this area.