I don't think this chart is particularly useful to understand the data, so I won't include it in our #COVID19 chart collection (https://blog.datawrapper.de/coronaviruscharts/). But I do think it offers an interesting perspective on China.
You can get some hover tooltips here: https://www.datawrapper.de/_/0j5Tg/
@lisacrost I can imagine this has to do more with when they decide to test someone than anything else, is that correct?