In general you are right that the dynamically created controls should be placed in Page_Init. However, since a Tab or a PageView are not controls but just parts of different controls like RadTabStrip or RadMultiPageView it will be too early in the page lifecycle for them to load if you place them in the Page_Init.
the Telerik team
Registration for Q1 2011 What’s New Webinar Week is now open. Mark your calendar for the week starting March 21st and book your seat
for a walk through all the exciting stuff we ship with the new release!