This is just about priorities and theirs are different to yours - firstly, we don't know that they don't have a system that catches and warns of possible errors, we only know that articles may be published without addressing them. Secondly, the fact that it was corrected post-publish suggests that errors are picked up, but timely publication is more important.

The core business is delivering news, and typos halting publication is not a trade-off they want to take, they'd rather have the subs or copy editors batch process or review all the corrections required - maybe they use Pull Requests? :D