Perhaps the "all at once" attack could work against today's hardware. This is because the mics (in devices I know of) are co-planar and the user may be speaking to Alexa (or whoever) from directly above or below the device. In this configuration, it is valid for all mics to be receiving the same audio signal simultaneously.

But in some future rev, one could imagine that if the mics in the array are non-coplanar (e.g. at least 4 mics) and sufficiently far from each other, then there is no possible way for the audio signal to reach them at once (unless it is actually light being measured).