Yea, that is nonsense. While the law says "Anyone who unlawfully damages or destroys another person's property is liable to a custodial sentence not exceeding two years or a monetary penalty." this basically never happens. He likely will get a small fine (if any).
Do actually get the 2 years you would have to do some very serious damage. As example a couple of years ago someone got 2 years (on probation) because he set fire to the restaurant he was working on.
You won't be locked up here for 2 years because you drilled a few holes in the wall...
2 years is insane for what seems like a harmless prank though. It′s maybe an issue with how law is defined, similar to stories when you become a sex offender by doing public urination. Perhaps those 2 drill holes are similar to ″unrepairable damage to historic object″.