When you have touch controls disabled via the app then you can still turn the mic on/off via the players' touch controls.
As a parent I'd like to disable Alexa etc now and then for various reasons, at the moment my only choice is to remove the voice service and re-add later.
I think it would be a good idea to include the mic button in the touch controls option, so when off you cannot turn the mic on/off, then add an extra option in the Sonos app to control the mic on/off.
This way you can disable Alexa without needing to remove the voice service.