Does Duplex neccessarily save recordings? i.e. does it save actual recordings of the called party's voice, or does it do real-time voice to text, never saving t

Does Duplex neccessarily save recordings? i.e. does it save actual recordings of the called party's voice, or does it do real-time voice to text, never saving the voice after it's decoded? Sure, there are going to be some ephemeral copies made in codecs, DSP's and such, but my cell phone does the same. Google may want recordings so they can evaluate the system after a call, but they don't have to make them.