The dynamic timeline is designed to help you stay calm especially in the early stages of a project, when uncertainties are at their greatest. When AI timing support is enabled, it applies a correction for the estimated inaccuracy of your timing to the dynamic timeline and to the timing screen. As time progresses and your work is gaining momentum, the weight of the correction is gradually reduced and more weight is given to your actual tracked progress.
In the early stages of a project, the dynamic timeline largely lines up with the gray vertical marker and barely accounts for your actual tracked progress. This reflects both uncertainty being common at the start of a project and the fact that more tasks might be added if it is still a long time until the scheduled end date. Only as time progresses will the timeline gradually take greater account of the actual amount of tasks completed, until matching the static timeline’s behavior when the project’s end date is reached.
You can choose to disable the dynamic timeline via Me > Settings > Dynamic Progress Bar. When disabled, the colored progress bar remains static with respect to time and always shows the ratio of tasks completed to all tasks defined in a project, as you would normally expect it to.