Nope, I programmed in AS for awhile though I left before Flex became well implemented.

I know about the movie clip system and don't deny what you claim. But now you're moving the goalposts as decoupling the elements from the Flash environment requires you to do more, well, hand coding. To do what you claim -- implement the same features with less code -- would require more handiwork inside the Flash authoring tool, which was never really a fun workflow even when Flash was more ubiquitous.

In any case, lowering the code count by relying on MovieClips, which as you say are basically libraries, hardly seems fair. I'm sure all the code in the OP could be reduced to about five lines, three of them being calls to external code and CSS files.