Hi Pheeraphat,
We have analyzed your scenario at our end, and this is the default behavior for DateTimeAxis and EmptyPointSettings. For your requirement, we have logged a feature request to implement DateTimeCategoryAxis. You can track the status of the feature from the below feedback link, and moreover, this feature will be included in our upcoming main release which is expected to be rolled out at the end of March 2021. Please be patience until then.
Thanks,
Dharanitharan. P