All these reports and speculation about the underlying issue are very interesting (and I am sure frustrating for those affected).
The Infotainment system is self-contained and glitches like those reported suggest that it was overloaded due to some kind of problem activity taking all its CPU resources: this could be an inherent bug that was triggered by an attempt to do an OTA, or some kind of normal server response when the car wakes up. My money is on the latter, since it is very unlikely everyone's car was trying to do an OTA at the same time - perhaps merely saying an OTA update was available was enough to trigger a bug, or beginning to download it did.
Actually doing an OTA would most likely require the car to not be driving and would take some time. This is how it works on most other vehicles.
Note that none of this should have affected the car's core driving systems and aids that don't use the Infotainment. They should still continue to function fine. The report of the car going backwards is probably coincidental report of the earlier (and oft mentioned) 1-pedal driving issue where the car can sometimes reverse and is likely not connected to this issue.
Of course features that depend on the Infotainment system, like the reversing camera, navigation, CarPlay/AA won't work properly in these situations, which can be considered "core" systems if you depend on them.
It is highly unlikely it was anything sinister. Far, far, far more likely it was an unexpected bug triggered by something someone changed on the server and it eventually got changed back.
Obviously it shouldn't have happened, and it doesn't speak well of MG's quality control processes. Hopefully lessons have been learned!
This was the whole reason why the OTA rollout is going to be slow, selective and focused on particular models as it comes. Would be nice to have a simple way to opt-out: but then again, I don't think the OTA updates will be automatic, they will be opt-in, I think it is likely something failed well before we got to the point of having that option. But still, some will want to have the option to "Never download any updates", it should be there.