Re: "unless they submit their skill to a full manual test run each day"
This bug means that Echo is not sending your app input where it was before.
I would compare it to having an iOS or Android app that requires input from the OS's keyboard, and suddenly the keyboard isn't working anymore.
If you are saying that developers need to check their skills for such a problem every day, that would be the equivalent of mobile developers having to test any feature of the mobile OS on which they require.
When Apple or Android releases new features, at least they are communicating about it. In this case Amazon is changing the behavior of the Echo without any communication. Its a stretch to blame this on the developers.