I would say it applies the same way. Hearing is still a human sense and we might argue it has more limitations than sight.
Imagine if Siri, Alexa or Cortana start giving me 10 options for action at one given time. Ups, I didn’t hear what was the 5th option due to disruption or lack of focus. Ah! Now the whole interaction needs to be repeated so I can hear all the options.
Do you think the response time will get slower and some frustration might arise? I certainly do.
That's why it is important to communicate clearly with normal speed and potentially respond with 1–2 options. Especially, when the technology is relatively new to the average user.
Remember the graph, the more trained the user is, the more stress and alternatives she can handle in short amount of time. That's why pilots, astronauts and similar professions are passing such rigorous training.
Of course, there are other limitations and concerns with voice UI and conversational interactions. It is a different way of transferring information from machine to human and vice versa . Nevertheless, the Hick's law is still valid.
That topic would make a nice article actually. :) Thanks for bringing it up Tony!