Yes that is the technical conclusion. But maybe the most important thing is that we have to do an actual teardown of the product in order to have some confidence that Amazon is not lying on it's Echo capabilities. To be clear, I am not saying we should trust Amazon & Co, I'm saying that if that's the level of trust we have with home assistance devices, why even bother with the stuff ?
This. It's why it's so important for laptops to permit a physical slider to block the integrated camera. It is a low-cost, low tech way to verify that the camera is not picking up usable images. The real problem is that we don't have something analogous for microphones. The best we could do is some kind of humming device that you could turn on near the sensor that would drown out any noises it might otherwise pick up…
It is definitely not low cost.
In the hardware business, we count pennies. We count fractions of pennies with the costs of various components.
A shutter means at least one extra mechanical part, and a more complicated housing and increased assembly time at the factory.
You might look at a piece of plastic and think it is only a few pennies of plastic. But by the time you get it integrated into the product, and shipped out to consumers, it can add up to a dollar of cost. That really eats into the profits of low-margin hardware.
Only if enough consumers care about hardware shutters does it make business sense to include it. If most don't, and it is not a part of their buying decision making, then you're just throwing away money. Especially if it leads to increased post-sales tech support costs: ("My camera doesn't work! Is the shutter closed? Oh it is!").
Note that this is not an argument not to have hardware shutters. They are a good thing. But they come at a significant (to the final price) cost.