Release burndown chart starting story points.
I have always been told that to size only a few items in the product backlog (maybe good for 1-2 sprints). This is basically a gradual process as what I have been told. Why do I see release burndown charts that start with "an original estimate at start" with a set amount of story points already assigned? Doesn't this defeat the purpose?
Doesn't this defeat the purpose?
Yes.
The reason you see those is because the people creating them do not understand the empirical nature of Scrum. They feel that using the terminologies and doing "sprints" means that they are using the Scrum framework. That is not always true. This statement appears in the Scrum Guide towards the end of the section that presents the Sprint.
Various practices exist to forecast progress, like burn-downs, burn-ups, or cumulative flows. While proven useful, these do not replace the importance of empiricism. In complex environments, what will happen is unknown. Only what has already happened may be used for forward-looking decision making.
Doesn't this defeat the purpose
Having a release burndown at all may defeat the purpose if it takes longer than one Sprint to produce a Done increment and to obtain empirical feedback. That could be something worth checking.