If you check TBA, 4607 is done playing for this year. That means they don’t have to meet all the rules with their robot any more. I’m assuming they are adding it for demo purposes or something like that.
That is actually an interesting solution for the audio. You will need to follow up with a power amp to feed the speaker. Several are available for a 12 volt supply. You could even use an old car radio and a small FM module to transmit sound to the robot from any source.