When text is animated ( create a text right click, create motion tween and the animate it, position for example), no virtual functions are called in the TimelineBuilder.
If it is a symbol we get a call to TimelineBuilder::AddMovieClip and then calls to UpdateDisplayTransform when there is a change.
Even weirder is that nothing is called at all when Text is animated. If you have a plain text not animated in one layer for in 5 frames for example. You will have in
ResourcePalette call to AddClassicText, in TimelineBuilder::AddClassicText, and 5 calls to ShowFrame.
When the text is animated no AddClassicText functions are called, and ShowFrame is called only once.