Measured, or merely observed? I wouldn't trust casual observation for something like this. In any case, there are other explanations for this than the feature

Measured, or merely observed? I wouldn't trust casual observation for something like this. In any case, there are other explanations for this than the feature doing what it says. Recording takes less power than constantly running a neural net over the audio to see if you said the trigger phrase. If you really don't trust the manufacturer, they could even artificially use excess power when the feature is enabled, just to make it look like it's doing something extra. Or they might not be listening to you 24/7, but only at selected times. There really is no way to verify that your phone isn't listening to you when it's not supposed to be.