The shirt looks staged on the model. Notice how the edges of the holes are all turned outward. And if it was done by hand, which is probably likely, was the cutter left handed or was the shirt cut inside out?
You’re right. Did they make small slits, then rip and slightly cut with a razor/box cutter to get uneven edges? Or gather together, winde and make small cuts? Have to practice on an old shirt. Easy to take a razor to a neckline.