Hi Derek Farr,
Greetings from Syncfusion.
Query 1: How do we keep the animation?
Currently, we are validating the reported issue we will let you know the complete details on or before the 8th Nov 2019.
Query 2: Is this how it is supposed to work where if we update the HeaderContent we have to manager everything ourselves?
Since the TabView is customized with the custom HeaderContent, any customizations such as changing the color of the selected tab, must be handled using the SelectionChanged event. Please let us know if you have any difficulties while using HeaderContent.