Trying to understand the graphs on wait times

When I look at the graphs on the website for a given day in the past, there are several markers - predicted times throughout the day, adjusted predictions, posted times, observed times. (And user submitted times - but there are VERY few of those).

The observed times are a light purple line. The posted time is a black dot.

The observed and posted are identical - ALWAYS. So that means what? That what Disney posts is always what the actual time is? Which would imply I should ignore what the TP app predicts - since the posted time is what TP is using to measuring how accurate their prediction is.

I understand the value of the prediction in planning and in advance of the time we get there - but once we approach the ride, I should ignore their prediction and simply use the posted time to determine what the wait will be?

And last point - if the observed and posted are always the same - why show two markers that mean exactly the same thing?

You might want to e-mail with this question. They are usually quick to respond, and will be able to give you the official answer.