His did_load looks okay to me given he is using load_view.
time.sleep can work, but it needs to be with code that has ui.in_background wrapped around it. Basically, for things on the ui thread, you will not see the ui update until the function exits. Ui.delay, or a Timer or Thread are recommended though, rather than in_background for something like this, if you care at all about precision. in_backgrounded coded gets run in a single queue, which can lead to surprising results if you think it behaves like an asynchronous thread.