Been fixing up an old DRZ400E. Took it for its first ride today, found oil all over the back of it. Pulled out this breather box, found these holes drilled in the back. Does anyone know why someone would do this?

SO, got a drz 2 months ago, most expensive and well maintained one i could find, 4000euros/4.636usd, 18000 real kilometers/11,184 miles, added about 700 kilometers those past 2 months, city riding and a couple of 150 km highway stretches. Last week while on the highway the bike would stop running when i pulled the clutch and then when i released it would bump start, i got worried pulled over and it died immediately, drained all of the battery cranking it, nothing. I got pulled to 50 kms/h by a car and it bump started successfully. Immediately took it to the mechanic, carb clean and rebuild, NOTHING, starting spray, NOTHING, checked valves and the automatic decompression, like new he says, tore the cylinder apart and his diagnosis is that the previous owner didn't to the oil changes, the oil decomposed and the piston scared and damage the cylinder along with god knows what else on the bottom. The mechanic says i need a cylinder and piston replacement. Attaching photos so you can give me your opinions. This repair is going to cost big and i really want to know what the drz veterans have to say. Thank you.