This behavior is designed to mimic the selection and navigation in windows explorer. The keyboard navigation is applied only to the current active row (a row that can be changed only through keyboard operations). Selecting a row with the mouse does not change the current active row of the keyboard navigation - that's why it remembers where it left off - and applies the keyboard operations to this row. Generally speaking operations with the mouse should not affect properties of the keyboard navigation.
Still you can achieve the desired behavior by handling the ItemClick event of the TreeList and changing the active row there:
rowElement = args.get_item().get_element();
//calling internal function to change the current active row
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