getUiElement is overridden in SparkPolymer to modify the parent class's behavior in order to retrieve the elements from the top-level widget's shadowDOM instead of the regular DOM. This is a temporary measure to make it possible for the two to coexist. getDialogElement was overridden in a similar way once, but in some iteration that went away.

Regarding the unenforced querySelector policy: 1) If people use it, they will break SparkPolymer 2) By the time people would want to use it, they would have presumably added something to spark.html, which means they'd already broken the Polymer UI living in spark_polymer.html and lib/polymer_ui/spark_polymer_ui.html. So I'd have to go and fix all of that anyway. 3) All of the above is hopefully going to last for one more week or so, after which we'll switch to Polymer for good.