Agree. I’ve only seen similar in pools that have been left unmaintained for months (winter, etc.). Gross, isn’t it? I think some tweets said it smelled bad, too. Yikes.
Also, testing a pool is quite easy. If you’re a professional, you might test every day. It’s easy to say, “Whoa! We have no chlorine!! That’s odd! I added a lot yesterday!” It should take about 24 hrs — maybe 48 hrs — to find out that H2O2 has been substituted for chlorine. And it should take 24 hrs — maybe 48 hrs — to get the balance back where it belongs.
Unless something else is going on. I mean: beyond total incompetence.