I will speculate three more things on this one. After re-reading the email this is my guess.
1. The email says the progress bar shows the time elapsed since we received your application. Now we need to see whether they use AOR date to do so or R10 check date. My guess is they will still be using AOR date.
2. The last line is "We’ll let you know when the progress bar is available for your application." It appears to me that this update may not be available for all applications at one go. It may appear for only certain kind of applications. If that is not the case not sure why they would put this line in email. It may mean nothing.
3. "It will give you an estimated completion date based on our latest estimated
processing times.". I think we need to keep an eye whether they are planning to update the estimated processing time. It has been showing 6 months since beginning of the year. It may be an attempt of changing this "6 month" window to something else as they move to 2019.
More than anything else I will be keeping an eye on the processing time on 12 Dec and hope and pray they just don't move the timeline to something else.