I read chromestatus every week or so and the intended landing date for this change caught me off guard.
I presume you're only human, so it's almost expected you will skip over a change as you don't think it's relevant or might even take days off work, in which case, it's easy to forget to read it. ChromeStatus is just one of the many signals you should use to filter issues before they reach customers.
Yes, we have CI (700+ machine hours for runs-on-master integration tests). No, we don't have a test that would have caught this (we are an app building platform and some of our features which our users use to deliver features to their users use iframes)