They could store data and then dump it later when the vehicle is being serviced. Unless their privacy states otherwise, assume data is being gathered and sold. Other car manufactures have been caught selling travel data. It's not even that paranoid. Google has been fined in the past for secretly collecting location data in Android when offline and then relaying it back to HQ once the phone got a signal.
How would they do that? I'm sure you can buy some sort of aerospace component that has the signal integrity to do radios, but it sounds expensive. There's a reason these kinds of components (e.g. muxes) aren't usually physical disconnections.
Automotive power relays are at least a thing, but they're expensive consumables that have significant power draw.
In either case they would have had to add the components at design time and do the physical validation/testing, not ship it as a software update.
I didn't notice until you mentioned it; fixed. Like others have pointed out, one issue has little to do with the other.
Cars were made for 100 years without an internet connection. Even for an EV there is no need for network connectivity or constant software updates. The first time a prominent figure is assasinated with a remote take-over of their vehicle people may start to see this issue a bit differently.
