Thank you for elaborating the issue. Yes indeed - this is how the ResourceHeaderCreated event is working by default. If you want to add your tooltip one ones you can check if the event is actually thrown after the Page_load event as in the code below:
sender, EventArgs e)
counter = 0;
sender, ResourceHeaderCreatedEventArgs e)
)).Text = e.Container.Resource.Text;
Hope this will explain the issue.
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