I don't think they are saying it was, unless I'm misreading. They're talking about standard ECS deploys. Yo add my anecdata, I do lots of ECS deploys via terraform into production and it works pretty seamlessly.
I don’t have a problem with deploys with CF. But it only let’s you configure a minimum healthy percentage. Which is good enough if you only need to validate that an instance is in an acceptable state via a health check.