CreationDate is an attribute of the System.Document entity while createdDate is a system attribute. The createdDate attribute is set by the Mendix Runtime once the object is created. CreationDate isn't touched by the Mendix Runtime, it is only filled when you use it in your model (a form or a microflow).
//Edit: Removed post and rephrased my comment
When I create a new project in 2.4.5 there is a CreationDate in the System.Document object. So both attributes can be selected, but only createdDate is filled with an actual date.
So my question still stands.
One of the modeler technicians told me that the conversion isn't causing this problem. The 'CreationDate' doesn't have any use at this point and can be selected in the 'connector'. The CreationDate attribute will be removed in a later version.