Agree the update itself is likely 30 minutes. But I think the real delay is Tesla creating the actual software build. Unless there's problems with the install.
I got to sit in my car yesterday and saw there were a few active alerts about Firmware mismatches between the "Vehicle Gateway" and the touchscreen, as well as the Telematics Control Unit mismatching with the vehicle. The alerts all mentioned something that it may have been caused by an unsuccessful or incomplete update. So maybe there's some issue applying the "30 minute update" but it might also be that it just doesn't exist yet. And, of course, the errors I saw might have been specific to my specific vehicle, and not indicating everyone's having those issues.