The foundation of our charting is based on the data that is collected. Depending on the chart, data collects at different times. The service that collects the data runs each night at midnight in the workspace timezone and collects data about the current state of iterations, releases, etc.
If the Release/Iteration creation date is later than the start date, which means the system do not collect any data since the release/iteration not exist yet. So user see the chart miss some data.