Oh man, that last thing bites me on a daily basis. The tldr is Google is trying and failing to recognize different people, and it used a different voice because

Oh man, that last thing bites me on a daily basis. The tldr is Google is trying and failing to recognize different people, and it used a different voice because the person it thought you were has their own assistant voice preferences set. Allegedly this is so you can tell it to turn off my lights and it knows what room you mean, or send information on a query to the correct phone. All this information and data Google sucks up about me and it can't even recognize my voice. Goes to your larger point about software being generally shit.