Re: Hopefully the hole was drilled from the outside
The hole was drilled from the inside, the bit skipped 15-20mm along the surface before biting, and the leak started while all the astronauts were asleep.
So either a crew member managed to get up and drill the hole during a sleep cycle without Mission Control or any other crew member noticing, or it happened during manufacture and somebody slapped a patch on it that started leaking a few months later.
The visible hole wasn't in the pressure hull either.
All the sane money is on a manufacturing defect in the pressure hull, and they drilled the hole to access the defect and squirt gunk over it.
Which eventually failed.
If roscosmos didn't have a totally disastrous management style, this would have been documented and known to NASA, they probably would have used the right kind of gunk so it wouldn't have leaked in the first place, and even if it had, the ISS crew would have been able to go straight to the leak and fix it immediately instead of searching for a few hours.
So yes, drilled on the ground.