30 pounds in 4 months would certainly be big progress in a short time for most people, but at his height, starting weight, and starting leanness, it's completely understandable. Not popular to say, but Starting Strength does those kinds of numbers all the time.
Did he gain bodyfat along the way? Obviously. But he also built muscle. Definitely not all muscle, but it's there. Maybe he's fatter now that you'd be comfortable being, but that's more your problem, not his.
What was his strength progress like over the four months? If he saw little to no significant strength gains, then I'd be more inclined to say he overdid the eating and/or underdid the training.
He was skinny with abs, now he's not. That's not necessarily "destroying" anything, especially if we think long term/big picture.
How old is this dude? Does he have a specific goal he's shooting for?
I'd work on addressing this more than his bodyfat.