I'm surprised not to see any milestones (or tasks set to 'show on roadmap') on your roadmap, it is these that tend to move between planned vs actual. Depending on the settings you are using, you will either have fixed start date or end date for the project so that will remain the same. Your actual also shows as green so is 'on track', which also means that the end date of the project is on target to be met so no reason why the bar would be different.
Try adding in some milestones/tasks onto the roadmap and I think you would see a clearer picture of how planned vs actual is different.
An example from my environment would be;