It’s a pointless “discovery”. They could probably do the same thing if they could hit the microphone on your cell phone except that’s always in your pocket. Being able to do something and having the opportunity to do it are not the same things. For you to fall victim to this exploit you’d need to put your Smart Speaker in line of sight of a window that could be used for the exploit, oriented so the microphone was visible, and you’d have to have something worth the effort of stealing because it’d be a lot of work. To do this you’d need a site where you can position and aim your laser to hit the speaker, undisturbed for however long it takes to accomplish the objective, remembering that you’re shooting the laser a fair distance so any error or movement at the source is going to equate to a large displacement at the target, and assuming the laser is solidly mounted and not subject to vibrations from, say, passing traffic, you still have to shoot it through a lot of air which can reduce the power arriving on target. And you’d want to use IR so no one could see your laser, but most windows are IR blocking for energy efficiency. It’d be far easier to just throw a rock through a window and break in.